Guest access to address spaces of adapter

ABSTRACT

An authorization mechanism allows a host executing a guest operating system to grant permission for the guest to directly access an adapter function&#39;s address spaces without host intervention. This access is via instructions implemented based on the architecture of the adapter function. The host also has the capability to intervene in the execution of the instruction, if desired.

BACKGROUND

This invention relates, in general, to input/output processing of a computing environment, and in particular, to virtual processing associated with adapters of the computing environment.

A computing environment may include one or more types of input/output devices, including various types of adapters. One type of adapter is a Peripheral Component Interconnect (PCI) or Peripheral Component Interconnect express (PCIe) adapter. This adapter includes one or more address spaces used in communicating data between the adapter and the system to which the adapter is attached.

In some systems, a portion of an address space of the central processing unit (CPU) coupled to the adapter is mapped to an address space of the adapter enabling CPU instructions that access storage to directly manipulate the data in the adapter's address space. This mapping of address spaces is sometimes referred to as memory-mapped I/O.

BRIEF SUMMARY

In one embodiment, direct access to an adapter's address space is provided to a guest operating system executing on a host without host intervention.

The shortcomings of the prior art are overcome and advantages are provided through the provision of a computer program product for providing access to adapters in a computing environment. The computer program product includes a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes, for instance, executing a guest instruction including a request to access an adapter; determining whether the guest instruction is permitted to directly access the adapter; responsive to being permitted, the execution directly accessing one or more address spaces of the adapter without host intervention; and responsive to not being permitted, the execution causing an intercept to a host operating system.

Methods and systems relating to one or more aspects of the present invention are also described and claimed herein. Further, services relating to one or more aspects of the present invention are also described and may be claimed herein.

Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more aspects of the present invention are particularly pointed out and distinctly claimed as examples in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1A depicts one embodiment of a computing environment to incorporate and use one or more aspects of the present invention;

FIG. 1B depicts one example of a device table entry used in accordance with an aspect of the present invention;

FIG. 1C depicts one embodiment of a central processing complex to incorporate and use one or more aspects of the present invention;

FIG. 2 depicts one example of address spaces of an adapter function, in accordance with an aspect of the present invention;

FIG. 3A depicts one example of a function table entry used in accordance with an aspect of the present invention;

FIG. 3B depicts one embodiment of a function handle used in accordance with an aspect of the present invention;

FIG. 4A depicts one example of a PCI Load instruction reading data from an adapter function, in accordance with an aspect of the present invention;

FIG. 4B depicts one embodiment of a PCI Store operation writing data to an adapter function, in accordance with an aspect of the present invention;

FIG. 4C depicts one embodiment of a Store Block operation writing data to an adapter function, in accordance with an aspect of the present invention;

FIG. 5 depicts one embodiment of initialization to be performed by the host to enable a guest direct access to address spaces of an adapter function, in accordance with an aspect of the present invention;

FIG. 6 depicts one embodiment of authorization processing performed on behalf of a guest, in accordance with an aspect of the present invention;

FIG. 7A depicts one embodiment of a Call Logical Processor instruction used in accordance with an aspect of the present invention;

FIG. 7B depicts one embodiment of a request block used by the Call Logical Processor instruction of FIG. 7A, in accordance with an aspect of the present invention;

FIG. 7C depicts one embodiment of a response block provided by the Call Logical Processor instruction of FIG. 7A, in accordance with an aspect of the present invention;

FIG. 8 depicts one embodiment of the logic to enable a PCI function, in accordance with an aspect of the present invention;

FIG. 9A depicts one embodiment of a Modify PCI Function Controls instruction used in accordance with an aspect of the present invention;

FIG. 9B depicts one embodiment of a field used by the Modify PCI Function Controls instruction of FIG. 9A, in accordance with an aspect of the present invention;

FIG. 9C depicts one embodiment of another field used by the Modify PCI Function Controls instruction of FIG. 9A, in accordance with an aspect of the present invention;

FIG. 9D depicts one embodiment of the contents of a function information block (FIB), used in accordance with an aspect of the present invention;

FIG. 10A depicts one embodiment of an overview of the logic of the Modify PCI Function Controls instruction, in accordance with an aspect of the present invention;

FIG. 10B depicts one embodiment of a set interception control operation that may be specified by the Modify PCI Function Controls instruction, in accordance with an aspect of the present invention;

FIG. 11A depicts one embodiment of a PCI Load instruction used in accordance with an aspect of the present invention;

FIG. 11B depicts one embodiment of a field used by the PCI Load instruction of FIG. 11A, in accordance with an aspect of the present invention;

FIG. 11C depicts one embodiment of another field used by the PCI Load instruction of FIG. 11A, in accordance with an aspect of the present invention;

FIGS. 12A-12B depict one embodiment of the logic to perform a PCI Load operation, in accordance with an aspect of the present invention;

FIG. 13A depicts one embodiment of a PCI Store instruction used in accordance with an aspect of the present invention;

FIG. 13B depicts one embodiment of a field used by the PCI Store instruction of FIG. 13A, in accordance with an aspect of the present invention;

FIG. 13C depicts one embodiment of another field used by the PCI Store instruction of FIG. 13A, in accordance with an aspect of the present invention;

FIGS. 14A-14B depict one embodiment of the logic to perform a PCI Store operation, in accordance with an aspect of the present invention;

FIG. 15A depicts one embodiment of a PCI Store Block instruction used in accordance with an aspect of the present invention;

FIG. 15B depicts one embodiment of a field used by the PCI Store Block instruction of FIG. 15A, in accordance with an aspect of the present invention;

FIG. 15C depicts one embodiment of another field used by the PCI Store Block instruction of FIG. 15A, in accordance with an aspect of the present invention;

FIG. 15D depicts one embodiment of yet another field used by the PCI Store Block instruction of FIG. 15A, in accordance with an aspect of the present invention;

FIGS. 16A-16B depict one embodiment of the logic to perform a PCI Store Block operation, in accordance with an aspect of the present invention;

FIG. 17 depicts one embodiment of a computer program product incorporating one or more aspects of the present invention;

FIG. 18 depicts one embodiment of a host computer system to incorporate and use one or more aspects of the present invention;

FIG. 19 depicts a further example of a computer system to incorporate and use one or more aspects of the present invention;

FIG. 20 depicts another example of a computer system comprising a computer network to incorporate and use one or more aspects of the present invention;

FIG. 21 depicts one embodiment of various elements of a computer system to incorporate and use one or more aspects of the present invention;

FIG. 22A depicts one embodiment of the execution unit of the computer system of FIG. 21 to incorporate and use one or more aspects of the present invention;

FIG. 22B depicts one embodiment of the branch unit of the computer system of FIG. 21 to incorporate and use one or more aspects of the present invention;

FIG. 22C depicts one embodiment of the load/store unit of the computer system of FIG. 21 to incorporate and use one or more aspects of the present invention; and

FIG. 23 depicts one embodiment of an emulated host computer system to incorporate and use one or more aspects of the present invention.

DETAILED DESCRIPTION

In one embodiment, an authorization capability is provided that allows a host (e.g., host operating system) executing a guest operating system to grant permission for the guest to directly access an adapter's address space without host intervention.

As used herein, the term adapter includes any type of adapter (e.g., storage adapter, network adapter, processing adapter, PCI adapter, cryptographic adapter, other type of input/output adapters, etc.). In one embodiment, an adapter includes one adapter function. However, in other embodiments, an adapter may include a plurality of adapter functions. One or more aspects of the present invention are applicable whether an adapter includes one adapter function or a plurality of adapter functions. Moreover, in the examples presented herein, adapter is used interchangeably with adapter function (e.g., PCI function) unless otherwise noted.

One embodiment of a computing environment to incorporate and use one or more aspects of the present invention is described with reference to FIG. 1A. In one example, a computing environment 100 is a System z® server offered by International Business Machines Corporation. System z® is based on the z/Architecture® offered by International Business Machines Corporation. Details regarding the z/Architecture® are described in an IBM® publication entitled, “z/Architecture Principles of Operation,” IBM Publication No. SA22-7832-07, February 2009, which is hereby incorporated herein by reference in its entirety. IBM®, System z® and z/Architecture® are registered trademarks of International Business Machines Corporation, Armonk, N.Y. Other names used herein may be registered trademarks, trademarks or product names of International Business Machines Corporation or other companies.

In one example, computing environment 100 includes one or more central processing units (CPUs) 102 coupled to a system memory 104 (a.k.a., main memory) via a memory controller 106. To access system memory 104, a central processing unit 102 issues a read or write request that includes an address used to access system memory. The address included in the request is typically not directly usable to access system memory, and therefore, it is translated to an address that is directly usable in accessing system memory. The address is translated via a translation mechanism (XLATE) 108. For example, the address is translated from a virtual address to a real or absolute address using, for instance, dynamic address translation (DAT).

The request, including the address (translated, if necessary), is received by memory controller 106. In one example, memory controller 106 is comprised of hardware and is used to arbitrate for access to the system memory and to maintain the memory's consistency. This arbitration is performed for requests received from CPUs 102, as well as for requests received from one or more adapters 110. Like the central processing units, the adapters issue requests to system memory 104 to gain access to the system memory.

In one example, adapter 110 is a Peripheral Component Interconnect (PCI) or PCI Express (PCIe) adapter that includes one or more PCI functions. A PCI function issues a request that is routed to an input/output hub 112 (e.g., a PCI hub) via one or more switches (e.g., PCIe switches) 114. In one example, the input/output hub is comprised of hardware, including one or more state machines, and is coupled to memory controller 106 via an I/O-to-memory bus 120.

The input/output hub includes, for instance, a root complex 116 that receives the request from a switch. The request includes an input/output address that is provided to an address translation and protection unit 118, which accesses information used for the request. As examples, the request may include an input/output address used to perform a direct memory access (DMA) operation or to request a message signaled interruption (MSI). Address translation and protection unit 118 accesses information used for the DMA or MSI request. As a particular example, for a DMA operation, information may be obtained to translate the address. The translated address is then forwarded to the memory controller to access system memory.

In one example, as described with reference to FIG. 1B, information used for the DMA or MSI request issued by an adapter is obtained from a device table entry (DTE) 130 of a device table 132 located in the I/O hub (e.g., in the address translation and protection unit). The device table entry includes information for the adapter, and each adapter has at least one device table entry associated therewith. For instance, there is one device table entry per address space (in system memory) assigned to the adapter. The information in the DTE may depend on the services provided to the adapter (e.g., address translation, interruptions, etc.) For a request issued from an adapter (e.g., PCI function 138), a device table entry is located using a requestor ID provided in the request.

Referring now to FIG. 1C, in a further embodiment of a computing environment, in addition to or instead of one or more of central processing units 102, a central processing complex is coupled to memory controller 106. In this particular example, central processing complex 150 provides virtual machine support. Central processing complex 150 includes, for instance, one or more virtual machines 152, one or more central processors 154, and at least one hypervisor 156, each of which is described below.

The virtual machine support of the central processing complex provides the ability to operate large numbers of virtual machines, each capable of hosting a guest operating system 158, such as z/Linux. Each virtual machine 152 is capable of functioning as a separate system. That is, each virtual machine can be independently reset, host a guest operating system, and operate with different programs. An operating system or application program running in a virtual machine appears to have access to a full and complete system, but in reality, only a portion of it is available.

In this particular example, the model of virtual machines is a V=V model, in which the memory of a virtual machine is backed by virtual memory, instead of real memory. Each virtual machine has a virtual linear memory space. The physical resources are owned by hypervisor 156, such as a VM hypervisor, and the shared physical resources are dispatched by the hypervisor to the guest operating systems, as needed, to meet their processing demands. This V=V virtual machine model assumes that the interactions between the guest operating systems and the physical shared machine resources are controlled by the VM hypervisor, since the large number of guests typically precludes the hypervisor from simply partitioning and assigning the hardware resources to the configured guest. One or more aspects of a V=V model are further described in an IBM publication entitled “z/VM: Running Guest Operating Systems,” IBM Publication No. SC24-5997-02, October 2001, which is hereby incorporated herein by reference in its entirety.

Central processors 154 are physical processor resources that are assignable to a virtual machine. For instance, virtual machine 152 includes one or more logical processors, each of which represents all or a share of a physical processor resource 154 that may be dynamically allocated to the virtual machine. Virtual machines 152 are managed by hypervisor 156. As examples, the hypervisor may be implemented in firmware running on processors 154 or may be a part of a host operating system executing on the machine. In one example, hypervisor 156 is a VM hypervisor, such as z/VM® offered by International Business Machines Corporation, Armonk, N.Y. One embodiment of z/VM® is described in an IBM publication entitled “z/VM: General Information Manual,” IBM Publication No. GC24-5991-05, May 2003, which is hereby incorporated herein by reference in its entirety.

As used herein, firmware includes, e.g., the microcode, millicode and/or macrocode of the processor. It includes, for instance, the hardware-level instructions and/or data structures used in implementation of higher-level machine code. In one embodiment, it includes, for instance, proprietary code that is typically delivered as microcode that includes trusted software or microcode specific to the underlying hardware and controls operating system access to the system hardware.

As described above, adapters can issue requests to the processors requesting various operations, such as direct memory accesses, message signaled interrupts, etc. Further, the processors can issue requests to the adapters. For instance, returning to FIG. 1B, a processor 102 can issue a request to access an adapter function 138. The request is routed from the processor to the adapter function via I/O hub 112 and one or more switches 114. In this embodiment, the memory controller is not shown. However, the I/O hub may be coupled to the processor directly or via a memory controller.

As an example, an operating system 140 executing within the processor issues an instruction to the adapter function requesting a particular operation. In this example, instructions issued by the operating system are specific to the I/O infrastructure. That is, since the I/O infrastructure is based on PCI or PCIe (both of which are referred to herein as PCI, unless otherwise noted), the instructions are PCI instructions. Example PCI instructions include PCI Load, PCI Store and PCI Store Block, to name a few. Although, in this example, the I/O infrastructure and instructions are based on PCI, in other embodiments, other infrastructures and corresponding instructions may be used.

In one particular example, the instructions are directed to a specific location within an address space of the adapter function. For instance, as shown in FIG. 2, an adapter function 138 includes storage 200, which is defined as a plurality of address spaces, including, for instance: a configuration space 202 (e.g., PCI configuration space for a PCI function); an I/O space 204 (e.g., PCI I/O space); and one or more memory spaces 206 (e.g., PCI memory space). In one embodiment, these address spaces are mapped into storage that is addressable only by the firmware. Thus, an abstraction of these spaces is presented to the operating system and accessible by the PCI instructions. The instructions are targeted to a particular address space and a particular location within the address space. This ensures that the configuration (e.g., operating system, LPAR, processor, guest, etc.) issuing the instruction is authorized to access the adapter function. In other embodiments, more, less or different address spaces may be provided.

To facilitate processing of the instructions, information stored in one or more data structures is used. One such data structure that includes information regarding adapters is a function table 300 stored, for instance, in secure memory. As shown in FIG. 3A, in one example, a function table 300 includes one or more function table entries (FTEs) 302. In one example, there is one function table entry per adapter function. Each function table entry 302 includes information to be used in processing associated with its adapter function. In one example, function table entry 302 includes, for instance:

-   -   Instance Number 308: This field indicates a particular instance         of the PCI function handle associated with the function table         entry;     -   Device Table Entry (DTE) Index 1 . . . n 310: There may be one         or more device table indices, and each index is an index into a         device table to locate a device table entry (DTE). There are one         or more device table entries per adapter function, and each         entry includes information associated with its adapter function,         including information used to process requests of the adapter         function (e.g., DMA requests, MSI requests) and information         relating to requests to the adapter function (e.g., PCI         instructions). Each device table entry is associated with one         address space within system memory assigned to the adapter         function. An adapter function may have one or more address         spaces within system memory assigned to the adapter function.     -   Busy Indicator 312: This field indicates whether the adapter         function is busy;     -   Permanent Error State Indicator 314: This field indicates         whether the adapter function is in a permanent error state;     -   Recovery Initiated Indicator 316: This field indicates whether         recovery has been initiated for the adapter function;     -   Permission Indicator 318: This field indicates whether the         operating system trying to enable the adapter function has         authority to do so;     -   Enable Indicator 320: This field indicates whether the adapter         function is enabled (e.g., 1=enabled, 0=disabled);     -   Requestor Identifier (RID) 322: This is an identifier of the         adapter function and may include, for instance, a bus number,         device number and function number.     -   This field is used, for instance, for accesses of a         configuration space of the adapter function. For instance, the         configuration space may be accessed by specifying the         configuration space in an instruction issued by the operating         system (or other configuration) to the adapter function.         Specified in the instruction is an offset into the configuration         space and a function handle used to locate the appropriate         function table entry that includes the RID. The firmware         receives the instruction and determines it is for a         configuration space. Therefore, it uses the RID to generate a         request to the I/O hub, and the I/O hub creates a request to         access the adapter. The location of the adapter function is         based on the RID, and the offset specifies an offset into the         configuration space of the adapter function.     -   Base Address Register (BAR) (1 to n) 324: This field includes a         plurality of unsigned integers, designated as BAR₀-BAR_(n),         which are associated with the originally specified adapter         function, and whose values are also stored in the base address         registers associated with the adapter function. Each BAR         specifies the starting address of a memory space or I/O space         within the adapter function, and also indicates the type of         address space, that is whether it is a 64 or 32 bit memory         space, or a 32 bit I/O space, as examples;     -   In one example, it is used for accesses to memory space and/or         I/O space of the adapter function. For instance, an offset         provided in an instruction to access the adapter function is         added to the value in the base address register associated with         the address space designated in the instruction to obtain the         address to be used to access the adapter function. The address         space identifier provided in the instruction identifies the         address space within the adapter function to be accessed and the         corresponding BAR to be used;     -   Size 1 . . . n 326: This field includes a plurality of unsigned         integers, designated as SIZE₀-SIZE_(n). The value of a Size         field, when non-zero, represents the size of each address space         with each entry corresponding to a previously described BAR.

Further details regarding BAR and Size are described below.

-   -   1. When a BAR is not implemented for an adapter function, the         BAR field and its corresponding size field are both stored as         zeros.     -   2. When a BAR field represents either an I/O address space or a         32-bit memory address space, the corresponding size field is         non-zero and represents the size of the address space.     -   3. When a BAR field represents a 64-bit memory address space,         -   a. The BAR_(n) field represents the least significant             address bits.         -   b. The next consecutive BAR_(n+1) field represents the most             significant address bits.         -   c. The corresponding SIZE_(n) field is non-zero and             represents the size of the address space.         -   d. The corresponding SIZE_(n+1) field is not meaningful and             is stored as zero.     -   Internal Routing Information 328: This information is used to         perform particular routing to the adapter. It includes, for         instance, node, processor chip, and hub addressing information,         as examples.     -   Status Indicator 330: This provides an indication of whether         load/store operations are blocked, as well as other indications.

In one example, the busy indicator, permanent error state indicator, and recovery initiated indicator are set based on monitoring performed by the firmware. Further, the permission indicator is set, for instance, based on policy. The BAR information is based on configuration information discovered during a bus walk by the processor (e.g., firmware of the processor). Other fields may be set based on configuration, initialization and/or events. In other embodiments, the function table entry may include more, less or different information. The information included may depend on the operations supported by or enabled for the adapter function.

To locate a function table entry in a function table that includes one or more entries, in one embodiment, a function handle is used. For instance, one or more bits of the function handle are used as an index into the function table to locate a particular function table entry.

Referring to FIG. 3B, additional details regarding a function handle are described. In one example, a function handle 350 includes an enable indicator 352 that indicates whether the PCI function handle is enabled; a PCI function number 354 that identifies the function (this is a static identifier, and in one embodiment, is an index into the function table); and an instance number 356 which indicates the particular instance of this function handle. For example, each time the handle is enabled, the instance number is incremented to provide a new instance number.

In one embodiment, adapter functions are initialized by the system firmware and assigned to an operating system or other configuration (as used herein, operating system includes device drivers). Subsequently, the operating system initializes each assigned function so that it can be used. For instance, the operating system first determines which adapter functions are assigned to the configuration. In one example, the operating system issues a list PCI functions command to make this determination. This command returns a list of function handles for the adapter functions assigned to the operating system. As an example, this information is retrieved from the function table. In particular, at initialization time, or after a hot plug of an adapter, firmware performs a bus walk to determine the location of the adapter and to determine its basic characteristics. This information is stored by the firmware into the function table entry for each adapter. It is then retrieved by the list command.

For each function handle returned by the list command, the operating system determines specific characteristics of the function designated by the handle. In one example, this is accomplished by issuing a query PCI function command that obtains this information from the function table entry. In a further example, characteristics common to a group of adapter functions is also obtained by, for instance, a query function group command. That is, group information based on a given system I/O infrastructure and the capabilities of the firmware and I/O hub may be stored in the function table entry (or other location) and retrieved by the query group command.

For each adapter function that the operating system wishes to use, the operating system enables the adapter function and obtains an enabled handle for that function. In one example, a set PCI function command of a Call Logical Processor (CLP) instruction is used to perform the enable. The enablement includes, for instance, performing one or more validity checks (e.g., of the function handle, function table entry, etc.) and setting an enable indicator in the function table entry, device table entry and function handle associated with the adapter function, responsive to passing the validity checks.

After enabling the function, various operational parameters are set in the device table entry and/or function table entry that are specific to the adapter function. In one example, a Modify PCI Function Controls instruction is used to set these parameters. Specifically, in one example, information is copied from a function information block to the device table entry and/or function table entry associated with the function. For example, a function information block designated in the Modify PCI Function Controls instruction is used to modify a selected device table entry and/or function table entry associated with the adapter function designated in the instruction. The parameters of the function information block that are used to modify the device table entry and/or function table entry are dependent on an operation control provided in the instruction. As examples, the operation control may specify registering/unregistering adapter interruptions, registering/unregistering address translation, reset error state, reset load/store block, set PCI function measurement parameters and set interception control.

After an adapter function has been enabled, as described above, one or more instructions may be used to provide the operating system the ability to configure the adapter function, to control the adapter function (initiate I/O operations), and to read its status. These instructions include, for instance, a PCI Load instruction, a PCI Store instruction, and a PCI Store Block instruction. These instructions interact with an adapter function's configuration, I/O and memory spaces, as follows:

-   -   As shown in FIG. 4A, the PCI Load instruction 400 allows, for         instance, the operating system executing on a CPU 401 to read up         to, e.g., 8 bytes of the contents of the PCI function's         configuration space 402, I/O space 404, or memory space 406 into         a general register 410.     -   For instance, during execution of the PCI Load instruction, a         number of validity checks are performed. If those checks are         successful, then processing continues with fetching the data         from a computed location in a specified address space of the         adapter function and returning the data in a response to the         load request. If the designated address space is a configuration         space, the RID is used to generate a configuration read request         used to fetch the data. However, if it is an I/O or memory         space, the BAR starting address obtained from the function table         entry is added to the offset provided in the instruction to         calculate a data address, which is used in a DMA read request         packet forwarded to the adapter function to fetch the data.     -   As shown in FIG. 4B, the PCI Store instruction 414 allows, for         instance, the operating system to write (i.e., alter) up to,         e.g., 8 bytes of the contents of a PCI function's configuration         space 402, I/O space 404, or memory space 406 from a general         register 416.     -   For instance, during execution of a PCI Store instruction, a         number of validity checks are performed. If successful,         processing continues with storing data at a specified location         in an address space of the adapter function. If the location in         which the data is to be stored is in the configuration space,         then the requestor ID obtained from the function table entry is         used to generate a configuration write request to the adapter         function. However, if the I/O address space or memory space is         to be stored into, then the BAR starting address obtained from         the function table entry is added to the offset provided in the         instruction to calculate a data address, which is included in a         DMA write request packet to the adapter function. The data is         then stored at the specified location.     -   As shown in FIG. 4C, the PCI Store Block instruction allows, for         instance, the operating system to write (i.e., alter), e.g., 32,         64, 128 or 256 bytes of a PCI function's memory space 406 from         main storage 420.

In accordance with an aspect of the present invention, an adapter function is to be virtualized for a guest (e.g., a pageable storage mode guest; i.e., a V=V guest) executing on a host (a.k.a., host program or host operating system). In one example, in the z/Architecture®, a pageable guest is interpretively executed via the Start Interpretive Execution (SIE) instruction, at level 2 of interpretation. For instance, the logical partition (LPAR) hypervisor executes the SIE instruction to begin the logical partition in physical, fixed memory. If z/VM® is the operating system in that logical partition, it issues the SIE instruction to execute its guests (virtual) machines in its V=V (virtual) storage. Therefore, the LPAR hypervisor uses level-1 SIE, and the z/VM® hypervisor uses level-2 SIE.

To virtualize the guest, the host authorizes the guest for the exclusive use of an adapter function assigned to the host. The authorization allows for the successful interpretation of various instructions, including the PCI Load, PCI Store and PCI Store Block instructions. That is, when these instructions are issued by a guest without error or exception, they execute without host intervention. Thus, interpretive execution entry and exit overhead, plus instruction emulation overhead by the host are eliminated for these instructions. This authorization mechanism is described below.

One embodiment of the logic associated with authorizing a guest to access an adapter function is described with reference to FIGS. 5 and 6. In particular, FIG. 5 depicts one embodiment of initialization to be performed by the host on behalf of the guest (e.g., guest processor), and FIG. 6 depicts one embodiment of authorization checks performed, responsive to a guest (e.g., guest processor) executing an instruction. In this embodiment, the instruction is a PCI instruction that is implemented specifically for PCI functions. In other embodiments, other instructions for other architectures may be used.

Referring to FIG. 5, initially, the host assigns one or more adapter functions for dedicated use by the guest, STEP 500. For instance, one or more of the adapter functions assigned to the host are assigned to the guest via, for instance, a table of assignments that indicates which adapter functions are associated with the guest or by a command that makes these associations, etc. The host intends for the PCI Load, PCI Store and PCI Store Block instructions, as examples, to be interpreted for the guest. Thus, the host performs certain initialization operations on behalf of a guest for each function that is assigned the guest, as described below. Other instructions that are not performance critical and control the configuration of the adapter (e.g., Modify PCI Function Controls) may typically be intercepted by the host.

For an assigned adapter function, STEP 502, the host authorizes the guest for interpretation of the PCI instructions by associating an authorization token with the adapter function, STEP 504. The authorization token is a unique token for the guest. In one particular example, it is a designation of a guest interruption state area (GISA), which is used during instruction execution to determine if the guest is permitted access to the adapter. In this embodiment, the GISA designation is a unique token, since there is one GISA per guest, regardless of how many virtual CPUs (state descriptions) comprise the guest. The GISA designation (e.g., a 32 bit value) is included in each state description, which is accessible by the host, but not by the guest. Although in one example, the GISA designation is used as the token, in another example, any unique value may be used.

In one example, the association of the authorization token is performed responsive to the guest executing a Call Logical Processor (CLP) set PCI function command, which intercepts to the host. The associating of the authorization token is accomplished by the host executing the Set PCI Function command on behalf of the guest and specifying the guest's GISA designation as the authorization token. During execution of the instruction, the GISA designation is copied from the command request block and placed in the function table entry associated with the adapter function being assigned. This is described more fully below.

Further, the host enables the guest for interpretation of the instructions for the adapter function, STEP 506. For instance, the host ensures that the interception control indicator in the function table entry for the adapter function is set to zero. In one example, a Modify PCI Function Controls instruction may be used to set this control, which is described further below.

Thereafter, if there are more functions to be assigned, INQUIRY 508, then processing returns to STEP 502. Otherwise, the host enables the guest for interpretation of the instructions for all adapter functions associated with the guest, STEP 510. In one example, this is performed by setting an interpretation indicator. This indicator is stored, for instance, in the state description(s) of the guest.

Subsequent to initialization and responsive to a guest executing an instruction, such as the PCI Load, PCI Store or PCI Store Block instruction, the instruction is interpreted, if certain checks are valid, including ensuring that the interpretation facility (referred to as PCI Load/Store interpretation) is installed in the host configuration. This is determined by an indicator set, for instance, in a control block. Further validity checks are described below with reference to FIG. 6.

In one embodiment, responsive to a guest (e.g., guest processor) executing one of the PCI instructions and assuming the facility is installed, STEP 602, a determination is made as to whether the guest is enabled for PCI Load/Store interpretation, INQUIRY 604. In particular, a control is provided in, for instance, a control block to allow a host to enable and disable the interpretation of the PCI instructions for all PCI functions assigned to a guest. If the control is set (e.g., to 1), the guest is enabled for PCI Load/Store interpretation. If the control is not set, then the guest is not enabled. The host can dynamically change this indicator from set to reset, when desired, to intervene in the execution of an instruction.

Further, another determination is made as to whether the adapter function is enabled for PCI Load/Store interpretation, INQUIRY 606. For example, a control is provided to allow a host to enable and disable the interpretation of the PCI instructions on a PCI function by PCI function basis. In one example, this control is an interception control indicator in the function table entry whose value is obtained from the function information block (which is provided as an operand of the Modify PCI Function Controls instruction, in one example). If in one example, this indicator is set, e.g., to 1, then a further determination is made as to whether the guest is authorized to issue the PCI Load, PCI Store, and PCI Store Block instructions for this adapter function, INQUIRY 608.

In one example, to determine if the guest is authorized to issue a PCI Load, PCI Store or PCI Store Block instruction for the specified adapter function, the authorization token is used. For instance, the value of the authorization token of the state description of the executing guest is compared to the authorization token that is in the FTE that was specified when the host enabled and authorized the guest (e.g., via the set PCI function command of the CLP instruction). If the guest is authorized, then a further determination is made as to whether the PCI function handle specified by the instruction operand (of the PCI instruction executed by the guest) is enabled, INQUIRY 610. In one example, this determination is made by checking the enable bit in the handle. If the function handle is enabled, then the guest can execute the PCI instructions without host intervention.

If any of the validity checks failed, however, then an interception to the host occurs, STEP 612. That is, the instruction is executed with host intervention.

Further details of the CLP set PCI function command are described herein. In order to use a PCI function, it is to be enabled. For instance, the operating system that would like to use a PCI function performs a query to determine the one or more functions that it is eligible to use (based on I/O configuration), and selects one of those functions to be enabled. In one example, the function is enabled using a set PCI function command of a Call Logical Processor instruction. One embodiment of this instruction is depicted in FIG. 7A. As shown, in one example, a Call Logical Processor instruction 700 includes an operation code 702 indicating that it is the Call Logical Processor instruction; and an indication for a command 704. In one example, this indication is an address of a request block that describes the command to be performed. One embodiment of such a request block is depicted in FIG. 7B.

As shown in FIG. 7B, in one example, a request block 720 includes a number of parameters, such as, for instance, a length field 722 indicating the length of the request block; a command field 724 indicating the set PCI function command; a PCI function handle 726, which is the handle to be provided to either the enable or disable function; an operation code 728, which is used to designate either an enable or disable operation; a number of DMA address spaces (DMAAS) 730, which indicates the requested number of address spaces to be associated with the particular PCI function; and a guest authorization token 732 used to authorize the guest. More, less or different information may be included in other embodiments. For instance, in a virtual environment in which the instruction is issued by a host of a pageable storage mode guest, a guest identity is provided. Other variations are also possible.

Responsive to issuing and processing the Call Logical Processor instruction, a response block is returned and the information included in the response block is dependent on the operation to be performed. One embodiment of the response block is depicted in FIG. 7C. In one example, response block 750 includes a length field 752 indicating the length of the response block; a response code 754 indicating a status of the command; and a PCI function handle 756 that identifies the PCI function. Responsive to the enable command, the PCI function handle is an enabled handle of the PCI function. Further, upon completion of the disable operation, the PCI function handle is a general handle that can be enabled by an enable function in the future.

One embodiment of the logic to enable a PCI function is described with reference to FIG. 8. In one example, this logic is initiated responsive to issuing a Call Logical Processor instruction in which the command is set to the set PCI function command and the operation code is set to the enable function. This logic is performed by, for instance, a processor responsive to the operating system or a device driver of the operating system authorized to perform this logic issuing the instruction. In other embodiments, the logic may be performed without the use of the Call Logical Processor instruction.

Referring to FIG. 8, initially, a determination is made as to whether a handle provided in the request block of the Call Logical Processor instruction is a valid handle, INQUIRY 800. That is, does the handle point to a valid entry in the function table or is it outside the range of valid entries (e.g., does the function number portion of the handle designate an installed function). If the handle is not known, then a corresponding response code is provided indicating that the handle is not recognized. However, if the handle is known, then a further inquiry is made as to whether the handle is enabled, INQUIRY 804. This determination is made by checking the enable indicator in the PCI function handle. If the indication is set indicating the handle is enabled, then a response code is returned indicating such, STEP 806.

However, if the handle is known and not enabled (i.e., valid for enablement), then a further determination is made as to whether the requested number of address spaces to be assigned to the PCI function is greater than a maximum value, INQUIRY 808. To make this determination, the number of DMA address spaces as specified in the request block is compared against a maximum value (provided based on policy, in one example). If the number of address spaces is greater than the maximum value, then a response code is provided indicating an invalid value for DMA address spaces, STEP 810. Otherwise, a determination is made as to whether the number of requested address spaces is available, INQUIRY 812. This determination is made by checking whether there are device table entries available for the requested number of address spaces. If the number of requested address spaces is not available, then a response code is returned indicating that there are insufficient resources, STEP 814. Otherwise, processing continues to enable the PCI function.

The provided handle is used to locate a function table entry, STEP 816. For instance, one or more designated bits of the handle are used as an index into the function table to locate a particular function table entry. Responsive to locating the appropriate function table entry, a determination is made as to whether the function is enabled, INQUIRY 818. This determination is made by checking the enable indicator in the function table entry. If the function is already enabled (i.e., the indicator is set to one), then a response code is returned indicating that the PCI function is already in the requested state, STEP 820.

If the function is not already enabled, then processing continues with determining whether the function is in a permanent error state, INQUIRY 822. If the permanent error state indicator in the function table entry indicates it is in a permanent error state, then a response code is returned indicating such, STEP 824. However, if the function is not in a permanent error state, a further determination is made as to whether error recovery has been initiated for the function, INQUIRY 826. If the recovery initiated indicator in the function table entry is set, then a response code indicating recovery has been initiated is provided, STEP 828. Otherwise, a further inquiry is made as to whether the PCI function is busy, INQUIRY 830. Again, if a check of the busy indicator in the function table entry indicates the PCI function is busy, then such an indication is provided, STEP 832. However, if the PCI function is not in the permanent error state, recovery is not initiated and it is not busy, then a further inquiry is made as to whether the operating system is permitted to enable this PCI function, STEP 834. If it is not permitted based on the permission indicator of the function table entry, then a response code indicating an unauthorized action is provided, STEP 836. However, if all the tests are successfully passed, then a further determination is made as to whether there are any DTEs available for this PCI function, INQUIRY 838. As examples, the determination of DTEs being available can be based on the DTEs that are not currently enabled in the I/O hub. Additionally, policy could be applied to further limit the number of DTEs available to a given operating system or logical partition. Any available DTE that is accessible to the adapter may be assigned. If there are no available DTEs, then a response code is returned indicating that one or more of the requested DTEs are unavailable, STEP 840.

If the DTEs are available, then a number of DTEs corresponding to the requested number of address spaces are assigned and enabled, STEP 842. In one example, the enabling includes setting the enable indicator in each DTE to be enabled. Further, the enabling includes, in this example, setting up a contents addressable memory (CAM) to provide an index to each DTE. For instance, for each DTE, an entry in the CAM is loaded with the index, and the CAM facilitates location of a DTE.

Further, the DTEs are associated with the function table entry, STEP 844. This includes, for instance, including each DTE index in the function table entry. The function is then marked as enabled by setting the enable indicator in the function table entry, STEP 846. Moreover, the enable bit in the handle is set, and the instance number is updated, STEP 848. This enabled handle is then returned, STEP 850, allowing use of the PCI adapter. For instance, responsive to enabling the function, registration for address translations and interruptions may be performed, DMA operations may be performed by the PCI function, and/or load, store and store block instructions may be issued to the function.

As indicated above, after enabling the function, various operational parameters are set in the DTE and/or FTE via, the Modify PCI Function Controls instruction. One example of the Modify PCI Function Controls instruction is described with reference to FIGS. 9A-9D.

Referring to FIG. 9A, a Modify PCI Function Controls instruction 900 includes, for instance, an op code 902 indicating the Modify PCI Function Controls instruction; a first field 904 specifying a location at which various information is included regarding the adapter function for which the operational parameters are being established; and a second field 906 specifying a location from which a PCI function information block (FIB) is fetched. The contents of the locations designated by Fields 1 and 2 are further described below.

In one embodiment, Field 1 designates a general register that includes various information. As shown in FIG. 9B, the contents of the register include, for instance, a function handle 910 that identifies the handle of the adapter function on behalf of which the modify instruction is being performed; an address space 912 designating an address space in system memory associated with the adapter function designated by the function handle; an operation control 914 which specifies the operation to be performed for the adapter function; and status 916 which provides status regarding the instruction when the instruction completes with a predefined code.

In one example, as shown in FIG. 9C, Field 2 designates a logical address 920 of a PCI function information block (FIB), which includes information regarding an associated adapter function. The function information block is used, in accordance with an aspect of the present invention, to update a device table entry and/or function table entry (or other location) associated with the adapter function. The information is stored in the FIB during initialization and/or configuration of the adapter, and/or responsive to a particular event.

Further details regarding a function information block are described with reference to FIG. 9D. In one embodiment, a function information block 950 includes the following fields:

-   -   Format 951: This field specifies the format of the FIB.     -   Interception Control 952: This field is used to indicate whether         guest execution of specific instructions by a pageable mode         guest results in instruction interception;     -   Error Indication 954: This field includes the error state         indication for direct memory access and adapter interruptions.         When the bit is set (e.g., 1), one or more errors have been         detected while performing direct memory access or adapter         interruption for the adapter function;     -   Load/Store Blocked 956: This field indicates whether load/store         operations are blocked;     -   PCI Function Valid 958: This field includes an enablement         control for the adapter function. When the bit is set (e.g., 1),         the adapter function is considered to be enabled for I/O         operations;     -   Address Space Registered 960: This field includes a direct         memory access enablement control for an adapter function. When         the field is set (e.g., 1) direct memory access is enabled;     -   Page Size 961: This field indicates the size of the page or         other unit of memory to be accessed by a DMA memory access;     -   PCI Base Address (PBA) 962: This field is a base address for an         address space in system memory assigned to the adapter function.         It represents the lowest virtual address that an adapter         function is allowed to use for direct memory access to the         specified DMA address space;     -   PCI Address Limit (PAL) 964: This field represents the highest         virtual address that an adapter function is allowed to access         within the specified DMA address space;     -   Input/Output Address Translation Pointer (IOAT) 966: The         input/output address translation pointer designates the first of         any translation tables used by a PCI virtual address         translation, or it may directly designate the absolute address         of a frame of storage that is the result of translation;     -   Interruption Subclass (ISC) 968: This field includes the         interruption subclass used to present adapter interruptions for         the adapter function;     -   Number of Interruptions (NOI) 970: This field designates the         number of distinct interruption codes accepted for an adapter         function. This field also defines the size, in bits, of the         adapter interruption bit vector designated by an adapter         interruption bit vector address and adapter interruption bit         vector offset fields;     -   Adapter Interruption Bit Vector Address (AIBV) 972: This field         specifies an address of the adapter interruption bit vector for         the adapter function. This vector is used in interrupt         processing;     -   Adapter Interruption Bit Vector Offset 974: This field specifies         the offset of the first adapter interruption bit vector bit for         the adapter function;     -   Adapter Interruption Summary Bit Address (AISB) 976: This field         provides an address designating the adapter interruption summary         bit, which is optionally used in interrupt processing;     -   Adapter Interruption Summary Bit Offset 978: This field provides         the offset into the adapter interruption summary bit vector;     -   Function Measurement Block (FMB) Address 980: This field         provides an address of a function measurement block used to         collect measurements regarding the adapter function;     -   Function Measurement Block Key 982: This field includes an         access key to access the function measurement block;     -   Summary Bit Notification Control 984: This field indicates         whether there is a summary bit vector being used;     -   Instruction Authorization Token 986: This field is used to         determine whether a pageable storage mode guest (e.g., V=V         guest) is authorized to execute PCI instructions without host         intervention; and     -   Address Translation Format 987: This field indicates a selected         format for address translation of the highest level translation         table to be used in translation (e.g., segment table, region         3rd, etc.).

The information in the function information block is obtained during configuration, initialization, and/or occurrence of a particular event.

The function information block designated in the Modify PCI Function Controls instruction is used, in accordance with an aspect of the present invention, to modify a selected device table entry, a function table entry and/or other firmware controls associated with the adapter function designated in the instruction. By modifying the device table entry, function table entry and/or other firmware controls, certain services are provided for the adapter. These services include, for instance, adapter interruptions; address translations; reset error state; reset load/store blocked; set function measurement parameters; and set interception control.

One embodiment of the logic associated with the Modify PCI Function Controls instruction is described with reference to FIG. 10A. In one example, the instruction is issued by an operating system (or other configuration) and executed by the processor (e.g., firmware) executing the operating system. In the examples herein, the instruction and adapter functions are PCI based. However, in other examples, a different adapter architecture and corresponding instructions may be used.

In one example, the operating system provides the following operands to the instruction (e.g., in one or more registers designated by the instruction): the PCI function handle; the DMA address space identifier; an operation control; and an address of the function information block.

Referring to FIG. 10A, initially, a determination is made as to whether the facility allowing for a Modify PCI Function Controls instruction is installed, INQUIRY 1000. This determination is made by, for instance, checking an indicator stored in, for instance, a control block. If the facility is not installed, an exception condition is provided, STEP 1002. Otherwise, a determination is made as to whether the instruction was issued by a pageable storage mode guest (or other guest), INQUIRY 1004. If yes, the host operating system will emulate the operation for that guest, STEP 1006. For instance, the host will intercept and determine if interception control is to be allowed for this guest. This determination is made by checking the FTE. If interception is authorized, the host will re-issue the Modify PCI Function Controls instruction on behalf of the guest. Otherwise, an exception condition is provided.

Otherwise, a determination is made as to whether one or more of the operands are aligned, INQUIRY 1008. For instance, a determination is made as to whether the address of the function information block is on a double word boundary. In one example, this is optional. If the operands are not aligned, then an exception condition is provided, STEP 1010. Otherwise, a determination is made as to whether the function information block is accessible, INQUIRY 1012. If not, then an exception condition is provided, STEP 1014. Otherwise, a determination is made as to whether the handle provided in the operands of the Modify PCI Function Controls instruction is enabled, INQUIRY 1016. In one example, this determination is made by checking an enable indicator in the handle. If the handle is not enabled, then an exception condition is provided, STEP 1018.

If the handle is enabled, then the handle is used to locate a function table entry, STEP 1020. That is, at least a portion of the handle is used as an index into the function table to locate the function table entry corresponding to the adapter function for which operational parameters are to be established.

A determination is made as to whether the function table entry was found, INQUIRY 1022. If not, then an exception condition is provided, STEP 1024. Otherwise, if the configuration issuing the instruction is a guest, INQUIRY 1026, then an exception condition (e.g., interception to the host) is provided, STEP 1028. This inquiry may be ignored if the configuration is not a guest or other authorizations may be checked, if designated.

A determination is then made as to whether the function is enabled, INQUIRY 1030. In one example, this determination is made by checking an enable indicator in the function table entry. If it is not enabled, then an exception condition is provided, STEP 1032.

If the function is enabled, then a determination is made as to whether recovery is active, INQUIRY 1034. If recovery is active as determined by a recovery indicator in the function table entry, then an exception condition is provided, 1036. However, if recovery is not active, then a further determination is made as to whether the function is busy, 1038. This determination is made by checking the busy indicator in the function table entry. If the function is busy, then a busy condition is provided, STEP 1040. With the busy condition, the instruction can be retried, instead of dropped.

If the function is not busy, then a further determination is made as to whether the function information block format is valid, INQUIRY 1042. For instance, the format field of the FIB is checked to determine if this format is supported by the system. If it is invalid, then an exception condition is provided, STEP 1044. If the function information block format is valid, then a further determination is made as to whether the operation control specified in the operands of the instruction is valid, INQUIRY 1046. That is, is the operation control one of the specified operation controls for this instruction. If it is invalid, then an exception condition is provided, STEP 1048. However, if the operation control is valid, then processing continues with the specific operation control being specified.

One operation that may be specified by an operation control of the Modify PCI Function Controls instruction is a set interception control operation used to control interruptions from adapters. With this operation, the PCI function parameters relative to interruption control are set from the interruption control field of the function information block. This operation control is considered to be reserved when issued by a pageable storage mode guest.

One embodiment of the logic of the set interception control operation is described with reference to FIG. 10B. In one example, the operand is the interception control from the function information block. Responsive to specifying this operation, the interception control in the function table entry is set to the interception control from the function information block, STEP 1060.

Subsequent to initialization, a guest may execute a PCI Load, PCI Store and PCI Store Block instruction, each of which is described below.

Referring initially to FIG. 11A, one embodiment of a PCI Load instruction is depicted. As shown, a PCI Load instruction 1100 includes, for instance, an opcode 1102 indicating the PCI Load instruction; a first field 1104 specifying a location at which data fetched from an adapter function will be loaded; and a second field 1106 specifying a location at which various information is included regarding the adapter function from which data is to be loaded. The contents of the locations designated by Fields 1 and 2 are further described below.

In one example, Field 1 designates a general register, and as depicted in FIG. 11B, the contents 1104 of that register include a contiguous range of one or more bytes loaded from the location of the adapter function specified in the instruction. In one example, the data is loaded into the rightmost byte positions of the register.

In one embodiment, Field 2 designates a pair of general registers that include various information. As shown in FIG. 11B, the contents of the registers include, for instance:

-   -   Enabled Handle 1110: This field is an enabled function handle of         the adapter function from which the data is to be loaded;     -   Address Space 1112: This field identifies the address space         within the adapter function from which the data is to be loaded;     -   Offset Within Address Space 1114: This field specifies the         offset within the specified address space from which the data is         to be loaded;     -   Length field 1116: This field specifies the length of the load         operation (e.g., the number of bytes to be loaded); and     -   Status field 1118: This field provides a status code which is         applicable when the instruction completes with a predefined         condition code.

In one embodiment, the bytes loaded from the adapter function are to be contained within an integral boundary in the adapter function's designated PCI address space. When the address space field designates a memory address space, the integral boundary size is, for instance, a double word. When the address space field designates an I/O address space or a configuration address space, the integral boundary size is, for instance, a word.

One embodiment of the logic associated with a PCI Load instruction is described with reference to FIGS. 12A-12B. In one example, the instruction is issued by an operating system (or other configuration) and executed by the processor (e.g., firmware) executing the operating system. In the examples herein, the instructions and adapter functions are PCI-based. However, in other examples, a different adapter architecture and corresponding instructions may be used.

To issue the instruction, the operating system provides the following operands to the instruction (e.g., in one or more registers designated by the instruction): the PCI function handle, the PCI address space (PCIAS), the offset into the PCI address space, and the length of the data to be loaded. Upon successful completion of the PCI Load instruction, the data is loaded in the location (e.g., register) designated by the instruction.

Referring to FIG. 12A, initially, a determination is made as to whether the facility allowing for a PCI Load instruction is installed, INQUIRY 1200. This determination is made by, for instance, checking an indicator stored in, for instance, a control block. If the facility is not installed, an exception condition is provided, STEP 1202. Otherwise, if a guest is issuing this instruction, a determination is made as to whether the guest is enabled for load/store interpretation. This is determined by checking the load/store interpretation control in the state description of the guest. If it is not enabled, an exception condition is provided. Otherwise, a determination is made as to whether the operands are aligned, INQUIRY 1204. For instance, if certain operands need to be in even/odd register pairs, a determination is made as to whether those requirements are met. If the operands are not aligned, then an exception is provided, STEP 1206. Otherwise, if the facility is installed and the operands are aligned, a determination is made as to whether the handle provided in the operands of the PCI Load instruction is enabled, INQUIRY 1208. In one example, this determination is made by checking an enable indicator in the handle. If the handle is not enabled, then an exception condition is provided, STEP 1210.

If the handle is enabled, then the handle is used to locate a function table entry, STEP 1212. That is, at least a portion of the handle is used as an index into the function table to locate the function table entry corresponding to the adapter function from which data is to be loaded.

Thereafter, a determination is made as to whether the instruction was issued by a guest, INQUIRY 1213. If so, then a further determination is made as to whether the interception control is set (e.g., to one), INQUIRY 1215. This determination is made by checking the interception control in the FTE. If it is set, then an exception condition is provided, STEP 1217. Otherwise, a determination is made as to whether the function is configured for use by a guest, INQUIRY 1214. If it is not authorized, then an exception condition is provided, STEP 1216. This inquiry may be ignored if the configuration is not a guest or other authorizations may be checked, if designated.

Thereafter, or if the instruction is not issued by a guest, a determination is then made as to whether the function is enabled, INQUIRY 1218. In one example, this determination is made by checking an enable indicator in the function table entry. If it is not enabled, then an exception condition is provided, STEP 1220.

If the function is enabled, then a determination is made as to whether the address space is valid, INQUIRY 1222. For instance, is the specified address space a designated address space of the adapter function and one that is appropriate for this instruction. If the address space is invalid, then an exception condition is provided, STEP 1224. Otherwise, a determination is made as to whether load/store is blocked, INQUIRY 1226. In one example, this determination is made by checking the status indicator in the function table entry. If load/store is blocked, then an exception condition is provided, STEP 1228.

However, if load/store is not blocked, a determination is made as to whether recovery is active, INQUIRY 1230. In one example, this determination is made by checking the recovery initiated indicator in the function table entry. If recovery is active, then an exception condition is provided, STEP 1232. Otherwise, a determination is made as to whether the function is busy, INQUIRY 1234. This determination is made by checking the busy indicator in the function table entry. If the function is busy, then a busy condition is provided, STEP 1236. With a busy condition, the instruction can be retried, instead of dropped.

If the function is not busy, then a further determination is made as to whether the offset specified in the instruction is valid, INQUIRY 1238. That is, is the offset in combination with the length of the operation within the base and length of the address space, as specified in the function table entry. If not, then an exception condition is provided, STEP 1240. However, if the offset is valid, then a determination is made as to whether the length is valid, INQUIRY 1242. That is, subject to the address space type, offset within the address space, and an integral boundary size is the length valid. If not, then an exception condition is provided, STEP 1244. Otherwise, processing continues with the load instruction. (In one embodiment, the firmware performs the above checks.)

Continuing with FIG. 12B, a determination is made by the firmware as to whether the load is for a configuration address space of the adapter function, INQUIRY 1250. That is, based on the configuration of the adapter function's memory, is the specified address space provided in the instruction a configuration space. If so, then the firmware performs various processing to provide the request to a hub coupled to the adapter function; the hub then routes the request to the function, STEP 1252.

For example, the firmware obtains the requestor ID from the function table entry pointed to by the function handle provided in the instruction operands. Further, the firmware determines based on information in the function table entry (e.g., the internal routing information) the hub to receive this request. That is, an environment may have one or more hubs and the firmware determines the hub coupled to the adapter function. It then forwards the request to the hub. The hub generates a configuration read request packet that flows out on the PCI bus to the adapter function identified by the RID in the function table entry. The configuration read request includes the RID and offset (i.e., data address) that are used to fetch the data, as described below.

Returning to INQUIRY 1250, if the designated address space is not a configuration space, then once again the firmware performs various processing to provide the request to the hub, STEP 1254. The firmware uses the handle to select a function table entry and from that entry it obtains information to locate the appropriate hub. It also calculates a data address to be used in the load operation. This address is calculated by adding the BAR starting address (with the BAR being that associated with the address space identifier provided in the instruction) obtained from the function table entry to the offset provided in the instruction. This calculated data address is provided to the hub. The hub then takes that address and includes it in a request packet, such as a DMA read request packet, that flows out over the PCI bus to the adapter function.

Responsive to receiving the request either via STEP 1252 or STEP 1254, the adapter function fetches the requested data from the specified location (i.e., at the data address) and returns that data in a response to the request, STEP 1256. The response is forwarded from the adapter function to the I/O hub. Responsive to receiving the response, the hub forwards the response to the initiating processor. The initiating processor then takes the data from the response packet and loads it in the designated location specified in the instruction (e.g., field 1 404). The PCI Load operation concludes with an indication of success (e.g., setting a condition code of zero).

In addition to a load instruction that retrieves data from an adapter function and stores it in a designated location, another instruction that may be executed is a store instruction. The store instruction stores data at a specified location in the adapter function. One embodiment of a PCI Store instruction is described with reference to FIG. 13A. As shown, a PCI Store instruction 1300 includes, for instance, an opcode 1302 indicating the PCI Store instruction; a first field 1304 specifying a location that includes data to be stored in an adapter function; and a second field 1306 specifying a location at which various information is included regarding the adapter function to which data is to be stored. The contents of the locations designated by Fields 1 and 2 are further described below.

In one example, Field 1 designates a general register, and as depicted in FIG. 13B, the contents 1304 of that register include a contiguous range of one or more bytes of data to be stored into the specified location of an adapter function. In one example, the data in the rightmost byte positions of the register are stored.

In one embodiment, Field 2 designates a pair of general registers that include various information. As shown in FIG. 13B, the contents of the register include, for instance:

-   -   Enabled Handle 1310: This field is an enabled function handle of         the adapter function to which the data is to be stored;     -   Address Space 1312: This field identifies the address space         within the adapter function to which the data is to be stored;     -   Offset Within Address Space 1314: This field specifies the         offset within the specified address space to which the data is         to be stored;     -   Length field 1316: This field specifies the length of the store         operation (e.g., the number of bytes to be stored); and     -   Status field 1318: This field provides a status code which is         applicable when the instruction completes with a predefined         condition code.

On embodiment of the logic associated with a PCI Store instruction is described with reference to FIGS. 14A-14B. In one example, the instruction is issued by an operating system, and executed by the processor (e.g., firmware) executing the operating system.

To issue the instruction, the operating system provides the following operands to the instruction (e.g., in one or more registers designated by the instruction): the PCI function handle, the PCI address space (PCIAS), the offset into the PCI address space, the length of the data to be stored, and a pointer to the data to be stored. Upon successful completion of the PCI Store instruction, the data is stored in the location designated by the instruction.

Referring to FIG. 14A, initially, a determination is made as to whether the facility allowing for a PCI Store instruction is installed, INQUIRY 1400. This determination is made by, for instance, checking an indicator stored in, for instance, a control block. If the facility is not installed, an exception condition is provided, STEP 1402. Otherwise, if a guest is issuing this instruction, a determination is made as to whether the guest is enabled for load/store interpretation. This is determined by checking the load/store interpretation control in the state description of the guest. If it is not enabled, an exception condition is provided. Otherwise, a determination is made as to whether the operands are aligned, INQUIRY 1404. For instance, if certain operands need to be in even/odd register pairs, a determination is made as to whether those requirements are met. If the operands are not aligned, then an exception is provided, STEP 1406. Otherwise, if the facility is installed and the operands are aligned, a determination is made as to whether the handle provided in the operands of the PCI Store instruction is enabled, INQUIRY 1408. In one example, this determination is made by checking an enable indicator in the handle. If the handle is not enabled, then an exception condition is provided, STEP 1410.

If the handle is enabled, then the handle is used to locate a function table entry, STEP 1412. That is, at least a portion of the handle is used as an index into the function table to locate the function table entry corresponding to the adapter function at which data is to be stored.

Thereafter, a determination is made as to whether the instruction was issued by a guest, INQUIRY 1413. If so, then a further determination is made as to whether the interception control is set (e.g., to one), INQUIRY 1415. This determination is made by checking the interception control in the FTE. If it is set, then an exception condition is provided, STEP 1417. Otherwise, a determination is made as to whether the function is configured for use by a guest, INQUIRY 1414. If it is not authorized, then an exception condition is provided, STEP 1416. This inquiry may be ignored if the configuration is not a guest or other authorizations may be checked, if designated.

Thereafter, or if the instruction is not issued by a guest, a determination is then made as to whether the function is enabled, INQUIRY 1418. In one example, this determination is made by checking an enable indicator in the function table entry. If it is not enabled, then an exception condition is provided, STEP 1420.

If the function is enabled, then a determination is made as to whether the address space is valid, INQUIRY 1422. For instance, is the specified address space a designated address space of the adapter function and one that is appropriate for this instruction. If the address space is invalid, then an exception condition is provided, STEP 1424. Otherwise, a determination is made as to whether load/store is blocked, INQUIRY 1426. In one example, this determination is made by checking the status indicator in the function table entry. If load/store is blocked, then an exception condition is provided, STEP 1428.

However, if the load/store is not blocked, a determination is made as to whether recovery is active, INQUIRY 1430. In one example, this determination is made by checking the recovery initiated indicator in the function table entry. If recovery is active, then an exception condition is provided, STEP 1432. Otherwise, a determination is made as to whether the function is busy, INQUIRY 1434. This determination is made by checking the busy indicator in the function table entry. If the function is busy, then a busy condition is provided, STEP 1436. With a busy condition, the instruction can be retried, instead of dropped.

If the function is not busy, then a further determination is made as to whether the offset specified in the instruction is valid, INQUIRY 1438. That is, is the offset in combination with the length of the operation within the base and length of the address space, as specified in the function table entry. If not, then an exception condition is provided, STEP 1440. However, if the offset is valid, then a determination is made as to whether the length is valid, INQUIRY 1442. That is, subject to the address space type, offset within the address space, and an integral boundary size is the length valid. If not, then an exception condition is provided, STEP 1444. Otherwise, processing continues with the store instruction. (In one embodiment, the firmware performs the above checks.)

Continuing with FIG. 14B, a determination is made by the firmware as to whether the store is for a configuration address space of the adapter function, INQUIRY 1450. That is, based on the configuration of the adapter function's memory, is the specified address space provided in the instruction a configuration space. If so, then the firmware performs various processing to provide the request to a hub coupled to the adapter function; the hub then routes the request to the function, STEP 1452.

For example, the firmware obtains the requestor id from the function table entry pointed to by the function handle provided in the instruction operands. Further, the firmware determines based on information in the function table entry (e.g., the internal routing information) the hub to receive this request. That is, an environment may have one or more hubs and the firmware determines the hub coupled to the adapter function. It then forwards the request to the hub. The hub generates a configuration write request packet that flows out on the PCI bus to the adapter function identified by the RID in the function table entry. The configuration write request includes the RID and offset (i.e., data address) that are used to store the data, as described below.

Returning to INQUIRY 1450, if the designated address space is not a configuration space, then once again the firmware performs various processing to provide the request to the hub, STEP 1454. The firmware uses the handle to select a function table entry and from that entry it obtains information to locate the appropriate hub. It also calculates a data address to be used in the store operation. This address is calculated by adding the BAR starting address obtained from the function table entry to the offset provided in the instruction. This calculated data address is provided to the hub. The hub then takes that address and includes it in a request packet, such as a DMA write request packet, that flows out over the PCI bus to the adapter function.

Responsive to receiving the request either via STEP 1452 or STEP 1454, the adapter function stores the requested data at the specified location (i.e., at the data address), STEP 1456. The PCI Store operation concludes with an indication of success (e.g., setting a condition code of zero).

In addition to the load and store instructions, which typically load or store a maximum of, e.g., 8 bytes, another instruction that may be executed is a store block instruction. The store block instruction stores larger blocks of data (e.g., 16, 32, 64, 128 or 256 bytes) at a specified location in the adapter function; the block sizes are not necessarily limited to powers of two in size. In one example, the specified location is in a memory space of the adapter function (not an I/O or configuration space).

One embodiment of a PCI Store Block instruction is described with reference to FIG. 15A. As shown, a PCI Store Block instruction 1500 includes, for instance, an opcode 1502 indicating the PCI Store Block instruction; a first field 804 specifying a location at which various information is included regarding the adapter function to which data is to be stored; a second field 1506 specifying a location that includes an offset within the specified address space into which the data is to be stored; and a third field 1508 specifying a location that includes a system memory address of data to be stored in the adapter function. The contents of the locations designated by Fields 1, 2 and 3 are further described below.

In one embodiment, Field 1 designates a general register that includes various information. As shown in FIG. 15B, the contents of the register include, for instance:

-   -   Enabled Handle 1510: This field is an enabled function handle of         the adapter function to which the data is to be stored;     -   Address Space 1512: This field identifies the address space         within the adapter function to which the data is to be stored;     -   Length field 1514: This field specifies the length of the store         operation (e.g., the number of bytes to be stored); and     -   Status field 1516: This field provides a status code which is         applicable when the instruction completes with a predefined         condition code.

In one example, Field 2 designates a general register, and as depicted in FIG. 15C, the contents of the register include a value (e.g., 64-bit unsigned integer) that specifies the offset within the specified address space into which the data is to be stored.

In one example, Field 3, as depicted in FIG. 15, includes the logical address of the first byte of data in system memory 1522 to be stored in the adapter function.

One embodiment of the logic associated with a PCI Store Block instruction is described with reference to FIGS. 16A-16B. In one example, the instruction is issued by an operating system, and executed by the processor (e.g., firmware) executing the operating system.

To issue the instruction, the operating system provides the following operands to the instruction (e.g., in one or more registers designated by the instruction): the PCI function handle, the PCI address space (PCIAS), the offset into the PCI address space, the length of the data to be stored, and a pointer to the data to be stored. The pointer operand may comprise both a register and a signed or unsigned displacement. Upon successful completion of the PCI Store Block instruction, the data is stored in the location in the adapter designated by the instruction.

Referring to FIG. 16A, initially, a determination is made as to whether the facility allowing for a PCI Store Block instruction is installed, INQUIRY 1600. This determination is made by, for instance, checking an indicator stored in, for instance, a control block. If the facility is not installed, an exception condition is provided, STEP 1602. Otherwise, if a guest is issuing this instruction, a determination is made as to whether the guest is enabled for load/store interpretation. This is determined by checking the load/store interpretation control in the state description of the guest. If it is not enabled, an exception condition is provided. Otherwise, if the facility is installed, a determination is made as to whether the handle provided in the operands of the PCI Store Block instruction is enabled, INQUIRY 1604. In one example, this determination is made by checking an enable indicator in the handle. If the handle is not enabled, then an exception condition is provided, STEP 1606.

If the handle is enabled, then the handle is used to locate a function table entry, STEP 1612. That is, at least a portion of the handle is used as an index into the function table to locate the function table entry corresponding to the adapter function at which data is to be stored.

Thereafter, a determination is made as to whether the instruction was issued by a guest, INQUIRY 1613. If so, then a further determination is made as to whether the interception control is set (e.g., to one), INQUIRY 1615. This determination is made by checking the interception control in the FTE. If it is set, then an exception condition is provided, STEP 1617. Otherwise, a determination is made as to whether the function is configured for use by a guest, INQUIRY 1614. If it is not authorized, then an exception condition is provided, STEP 1616. This inquiry may be ignored if the configuration is not a guest or other authorizations may be checked, if designated.

Thereafter, or if the instruction is not issued by a guest, a determination is then made as to whether the function is enabled, INQUIRY 1618. In one example, this determination is made by checking an enable indicator in the function table entry. If it is not enabled, then an exception condition is provided, STEP 1620.

If the function is enabled, then a determination is made as to whether the address space is valid, INQUIRY 1622. For instance, is the specified address space a designated address space of the adapter function and one that is appropriate for this instruction (i.e., a memory space). If the address space is invalid, then an exception condition is provided, STEP 1624. Otherwise, a determination is made as to whether load/store is blocked, INQUIRY 1626. In one example, this determination is made by checking the status indicator in the function table entry. If load/store is blocked, then an exception condition is provided, STEP 1628.

However, if the load/store is not blocked, a determination is made as to whether recovery is active, INQUIRY 1630. In one example, this determination is made by checking the recovery initiated indicator in the function table entry. If recovery is active, then an exception condition is provided, STEP 1632. Otherwise, a determination is made as to whether the function is busy, INQUIRY 1634. This determination is made by checking the busy indicator in the function table entry. If the function is busy, then a busy condition is provided, STEP 1636. With a busy condition, the instruction can be retried, instead of dropped.

If the function is not busy, then a further determination is made as to whether the offset specified in the instruction is valid, INQUIRY 1638. That is, is the offset in combination with the length of the operation within the base and length of the address space, as specified in the function table entry. If not, then an exception condition is provided, STEP 1640. However, if the offset is valid, then a determination is made as to whether the length is valid, INQUIRY 1642. That is, subject to the address space type, offset within the address space, and an integral boundary size is the length valid. If not, then an exception condition is provided, STEP 1644. Otherwise, processing continues with the store block instruction. (In one embodiment, the firmware performs the above checks.)

Continuing with FIG. 16B, a determination is made by the firmware as to whether the storage that includes the data to be stored is accessible, INQUIRY 1650. If not, an exception condition is provided, STEP 1652. If so, then the firmware performs various processing to provide the request to a hub coupled to the adapter function; the hub then routes the request to the function, STEP 1654.

For example, the firmware uses the handle to select a function table entry and from that entry it obtains information to locate the appropriate hub. It also calculates a data address to be used in the store block operation. This address is calculated by adding the BAR starting address (with the BAR being identified by the address space identifier) obtained from the function table entry to the offset provided in the instruction. This calculated data address is provided to the hub. In addition, the data referenced by the address provided in the instruction is fetched from system memory and provided to the I/O hub. The hub then takes that address and data and includes it in a request packet, such as a DMA write request packet, that flows out over the PCI bus to the adapter function.

Responsive to receiving the request, the adapter function stores the requested data at the specified location (i.e., at the data address), STEP 1656. The PCI Store Block operation concludes with an indication of success (e.g., setting a condition code of zero).

Described in detail above is an authorization capability that enables a host executing a guest to grant permission for the guest to directly access an adapter's address space(s) without host intervention. These address spaces are not mapped into the memory space seen by the operating system (guest or host). Instead, they are abstracted (i.e., made available by specific PCI instructions). When the guest is executing under interpretative execution, the adapter function assigned to the guest is “owned” by the guest, and therefore, may be manipulated directly by execution of guest instructions (e.g., PCI Load and PCI Store functions) without host intervention when authorized. Further, when the guest is executing under interpretative execution, guest instruction storage and operand addresses are treated as logical addresses and the addressed storage may be manipulated directly by the execution of the guest instruction (e.g., PCI Store Block when authorized) without host intervention. In one example, the guest is in supervisor state to execute the instructions.

The interpretation controls give the host control over PCI instruction interpretation at both the guest and function level. There may be a mix of simulated (i.e., software representation of a device) and dedicated devices (i.e., hardware devices). For simulated devices, there are no interception controls. Guest PCI Load/Store instructions would intercept to the host; and the host would maintain a version of the FTE and DTE to maintain the status to make it look to a guest as if the devices was there.

Moreover, if the host decides that it wishes to intervene, then it may do so, dynamically (including during instruction execution).

In the embodiments described herein, the adapters are PCI adapters. PCI, as used herein, refers to any adapters implemented according to a PCI-based specification as defined by the Peripheral Component Interconnect Special Interest Group (PCI-SIG), including but not limited to, PCI or PCIe. In one particular example, the Peripheral Component Interconnect Express (PCIe) is a component level interconnect standard that defines a bi-directional communication protocol for transactions between I/O adapters and host systems. PCIe communications are encapsulated in packets according to the PCIe standard for transmission on a PCIe bus. Transactions originating at I/O adapters and ending at host systems are referred to as upbound transactions. Transactions originating at host systems and terminating at I/O adapters are referred to as downbound transactions. The PCIe topology is based on point-to-point unidirectional links that are paired (e.g., one upbound link, one downbound link) to form the PCIe bus. The PCIe standard is maintained and published by the PCI-SIG.

Other applications filed on the same day include: U.S. Ser. No. 12/821,170, entitled “Translation Of Input/Output Addresses To Memory Addresses,” Craddock et al., (POU920090029US1); U.S. Ser. No. 12/821,171, entitled “Runtime Determination Of Translation Formats For Adapter Functions,” Craddock et al., (POU920100007US1); U.S. Ser. No. 12/821,172, entitled “Resizing Address Spaces Concurrent To Accessing The Address Spaces,” Craddock et al., (POU920100009US1); U.S. Ser. No. 12/821,174, entitled “Multiple Address Spaces Per Adapter,” Craddock et al., (POU920100010US1); U.S. Ser. No. 12/821,175, entitled “Converting A Message Signaled Interruption Into An I/O Adapter Event Notification,” Craddock et al., (POU920100014US1); U.S. Ser. No. 12/821,177, entitled “Converting A Message Signaled Interruption Into An I/O Adapter Event Notification To A Guest Operating System,” Brice et al., (POU920100015US1); U.S. Ser. No. 12/821,178, entitled “Identification Of Types Of Sources Of Adapter Interruptions,” Craddock et al., (POU920100016US1); U.S. Ser. No. 12/821,179, entitled “Controlling A Rate At Which Adapter Interruption Requests Are Processed,” Belmar et al., (POU920100017US1); U.S. Ser. No. 12/821,181, entitled “Controlling The Selectively Setting Of Operational Parameters For An Adapter,” Craddock et al., (POU920100018US1); U.S. Ser. No. 12/821,182, entitled “Load Instruction for Communicating with Adapters,” Craddock et al., (POU920100019US1); U.S. Ser. No., 12/821,184, entitled “Controlling Access By A Configuration To An Adapter Function,” Craddock et al., (POU920100020US1); U.S. Ser. No. 12/821,185, entitled “Discovery By Operating System Of Information Relating To Adapter Functions Accessible To The Operating System,” Coneski et al., (POU920100021US1); U.S. Ser. No. 12/821,187, entitled “Enable/Disable Adapters Of A Computing Environment,” Coneski et al., (POU920100022US1); U.S. Ser. No. 12/821,191, entitled “Managing Processing Associated With Hardware Events,” Coneski et al., (POU920100025US1); U.S. Ser. No. 12/821,192, entitled “Operating System Notification Of Actions To Be Taken Responsive To Adapter Events,” Craddock et al., (POU920100026US1); U.S. Ser. No. 12/821,193, entitled “Measurement Facility For Adapter Functions,” Brice et al., (POU920100027US1); U.S. Ser. No. 12/821,648, entitled “Store/Store Block Instructions for Communicating with Adapters,” Craddock et al., (POU920100162US1); U.S. Ser. No. 12/821,224, entitled “Associating Input/Output Device Requests With Memory Associated With A Logical Partition,” Craddock et al., (POU920100045US1); U.S. Ser. No. 12/821,247, entitled “Scalable I/O Adapter Function Level Error Detection, Isolation, And Reporting,” Craddock et al., (POU920100044US1); U.S. Ser. No. 12/821,256, entitled “Switch Failover Control In A Multiprocessor Computer System,” Bayer et al., (POU920100042US1); U.S. Ser. No. 12/821,242, entitled “A System And Method For Downbound I/O Expansion Request And Response Processing In A PCIe Architecture,” Gregg et al., (POU920100040US1); U.S. Ser. No. 12/821,243, entitled “Upbound Input/Output Expansion Request And Response Processing In A PCIe Architecture,” Gregg et al., (POU920100039US1); U.S. Ser. No. 12/821,245, entitled “A System And Method For Routing I/O Expansion Requests And Responses In A PCIe Architecture,” Lais et al. (POU920100038US1); U.S. Ser. No. 12/821,239, entitled “Input/Output (I/O) Expansion Response Processing In A Peripheral Component Interconnect Express (PCIe) Environment,” Gregg et al., (POU920100037US1); U.S. Ser. No. 12/821,271, entitled “Memory Error Isolation And Recovery In A Multiprocessor Computer System,” Check et al., (POU920100041US1); and U.S. Ser. No. 12/821,24867, entitled “Connected Input/Output Hub Management,” Bayer et al., (POU920100036US1), each of which is hereby incorporated herein by reference in its entirety.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system”. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

Referring now to FIG. 17, in one example, a computer program product 1700 includes, for instance, one or more computer readable storage media 1702 to store computer readable program code means or logic 1704 thereon to provide and facilitate one or more aspects of the present invention.

Program code embodied on a computer readable medium may be transmitted using an appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language, such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language, assembler or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

In addition to the above, one or more aspects of the present invention may be provided, offered, deployed, managed, serviced, etc. by a service provider who offers management of customer environments. For instance, the service provider can create, maintain, support, etc. computer code and/or a computer infrastructure that performs one or more aspects of the present invention for one or more customers. In return, the service provider may receive payment from the customer under a subscription and/or fee agreement, as examples. Additionally or alternatively, the service provider may receive payment from the sale of advertising content to one or more third parties.

In one aspect of the present invention, an application may be deployed for performing one or more aspects of the present invention. As one example, the deploying of an application comprises providing computer infrastructure operable to perform one or more aspects of the present invention.

As a further aspect of the present invention, a computing infrastructure may be deployed comprising integrating computer readable code into a computing system, in which the code in combination with the computing system is capable of performing one or more aspects of the present invention.

As yet a further aspect of the present invention, a process for integrating computing infrastructure comprising integrating computer readable code into a computer system may be provided. The computer system comprises a computer readable medium, in which the computer medium comprises one or more aspects of the present invention. The code in combination with the computer system is capable of performing one or more aspects of the present invention.

Although various embodiments are described above, these are only examples. For example, computing environments of other architectures can incorporate and use one or more aspects of the present invention. As examples, servers other than System z® servers, such as Power Systems servers or other servers offered by International Business Machines Corporation, or servers of other companies can include, use and/or benefit from one or more aspects of the present invention. Further, although in the example herein, the adapters and PCI hub are considered a part of the server, in other embodiments, they do not have to necessarily be considered a part of the server, but can simply be considered as being coupled to system memory and/or other components of a computing environment. The computing environment need not be a server. Further, although tables are described, any data structure can be used and the term table is to include all such data structures. Yet further, although the adapters are PCI based, one or more aspects of the present invention are usable with other adapters or other I/O components. Adapter and PCI adapter are just examples. Moreover, the DTE, FTE, FIB and/or other structures may include more, less or different data. Many other variations are possible.

Further, other types of computing environments can benefit from one or more aspects of the present invention. As an example, a data processing system suitable for storing and/or executing program code is usable that includes at least two processors coupled directly or indirectly to memory elements through a system bus. The memory elements include, for instance, local memory employed during actual execution of the program code, bulk storage, and cache memory which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution.

Input/Output or I/O devices (including, but not limited to, keyboards, displays, pointing devices, DASD, tape, CDs, DVDs, thumb drives and other memory media, etc.) can be coupled to the system either directly or through intervening I/O controllers. Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modems, and Ethernet cards are just a few of the available types of network adapters.

Referring to FIG. 18, representative components of a Host Computer system 5000 to implement one or more aspects of the present invention are portrayed. The representative host computer 5000 comprises one or more CPUs 5001 in communication with computer memory (i.e., central storage) 5002, as well as I/O interfaces to storage media devices 5011 and networks 5010 for communicating with other computers or SANs and the like. The CPU 5001 is compliant with an architecture having an architected instruction set and architected functionality. The CPU 5001 may have dynamic address translation (DAT) 5003 for transforming program addresses (virtual addresses) into real addresses of memory. A DAT typically includes a translation lookaside buffer (TLB) 5007 for caching translations so that later accesses to the block of computer memory 5002 do not require the delay of address translation. Typically, a cache 5009 is employed between computer memory 5002 and the processor 5001. The cache 5009 may be hierarchical having a large cache available to more than one CPU and smaller, faster (lower level) caches between the large cache and each CPU. In some implementations, the lower level caches are split to provide separate low level caches for instruction fetching and data accesses. In one embodiment, an instruction is fetched from memory 5002 by an instruction fetch unit 5004 via a cache 5009. The instruction is decoded in an instruction decode unit 5006 and dispatched (with other instructions in some embodiments) to instruction execution unit or units 5008. Typically several execution units 5008 are employed, for example an arithmetic execution unit, a floating point execution unit and a branch instruction execution unit. The instruction is executed by the execution unit, accessing operands from instruction specified registers or memory as needed. If an operand is to be accessed (loaded or stored) from memory 5002, a load/store unit 5005 typically handles the access under control of the instruction being executed. Instructions may be executed in hardware circuits or in internal microcode (firmware) or by a combination of both.

As noted, a computer system includes information in local (or main) storage, as well as addressing, protection, and reference and change recording. Some aspects of addressing include the format of addresses, the concept of address spaces, the various types of addresses, and the manner in which one type of address is translated to another type of address. Some of main storage includes permanently assigned storage locations. Main storage provides the system with directly addressable fast-access storage of data. Both data and programs are to be loaded into main storage (from input devices) before they can be processed.

Main storage may include one or more smaller, faster-access buffer storages, sometimes called caches. A cache is typically physically associated with a CPU or an I/O processor. The effects, except on performance, of the physical construction and use of distinct storage media are generally not observable by the program.

Separate caches may be maintained for instructions and for data operands. Information within a cache is maintained in contiguous bytes on an integral boundary called a cache block or cache line (or line, for short). A model may provide an EXTRACT CACHE ATTRIBUTE instruction which returns the size of a cache line in bytes. A model may also provide PREFETCH DATA and PREFETCH DATA RELATIVE LONG instructions which effects the prefetching of storage into the data or instruction cache or the releasing of data from the cache.

Storage is viewed as a long horizontal string of bits. For most operations, accesses to storage proceed in a left-to-right sequence. The string of bits is subdivided into units of eight bits. An eight-bit unit is called a byte, which is the basic building block of all information formats. Each byte location in storage is identified by a unique nonnegative integer, which is the address of that byte location or, simply, the byte address. Adjacent byte locations have consecutive addresses, starting with 0 on the left and proceeding in a left-to-right sequence. Addresses are unsigned binary integers and are 24, 31, or 64 bits.

Information is transmitted between storage and a CPU or a channel subsystem one byte, or a group of bytes, at a time. Unless otherwise specified, in, for instance, the z/Architecture®, a group of bytes in storage is addressed by the leftmost byte of the group. The number of bytes in the group is either implied or explicitly specified by the operation to be performed. When used in a CPU operation, a group of bytes is called a field. Within each group of bytes, in, for instance, the z/Architecture®, bits are numbered in a left-to-right sequence. In the z/Architecture®, the leftmost bits are sometimes referred to as the “high-order” bits and the rightmost bits as the “low-order” bits. Bit numbers are not storage addresses, however. Only bytes can be addressed. To operate on individual bits of a byte in storage, the entire byte is accessed. The bits in a byte are numbered 0 through 7, from left to right (in, e.g., the z/Architecture). The bits in an address may be numbered 8-31 or 40-63 for 24-bit addresses, or 1-31 or 33-63 for 31-bit addresses; they are numbered 0-63 for 64-bit addresses. Within any other fixed-length format of multiple bytes, the bits making up the format are consecutively numbered starting from 0. For purposes of error detection, and in preferably for correction, one or more check bits may be transmitted with each byte or with a group of bytes. Such check bits are generated automatically by the machine and cannot be directly controlled by the program. Storage capacities are expressed in number of bytes. When the length of a storage-operand field is implied by the operation code of an instruction, the field is said to have a fixed length, which can be one, two, four, eight, or sixteen bytes. Larger fields may be implied for some instructions. When the length of a storage-operand field is not implied but is stated explicitly, the field is said to have a variable length. Variable-length operands can vary in length by increments of one byte (or with some instructions, in multiples of two bytes or other multiples). When information is placed in storage, the contents of only those byte locations are replaced that are included in the designated field, even though the width of the physical path to storage may be greater than the length of the field being stored.

Certain units of information are to be on an integral boundary in storage. A boundary is called integral for a unit of information when its storage address is a multiple of the length of the unit in bytes. Special names are given to fields of 2, 4, 8, and 16 bytes on an integral boundary. A halfword is a group of two consecutive bytes on a two-byte boundary and is the basic building block of instructions. A word is a group of four consecutive bytes on a four-byte boundary. A doubleword is a group of eight consecutive bytes on an eight-byte boundary. A quadword is a group of 16 consecutive bytes on a 16-byte boundary. When storage addresses designate halfwords, words, doublewords, and quadwords, the binary representation of the address contains one, two, three, or four rightmost zero bits, respectively. Instructions are to be on two-byte integral boundaries. The storage operands of most instructions do not have boundary-alignment requirements.

On devices that implement separate caches for instructions and data operands, a significant delay may be experienced if the program stores into a cache line from which instructions are subsequently fetched, regardless of whether the store alters the instructions that are subsequently fetched.

In one embodiment, the invention may be practiced by software (sometimes referred to licensed internal code, firmware, micro-code, milli-code, pico-code and the like, any of which would be consistent with the present invention). Referring to FIG. 18, software program code which embodies the present invention is typically accessed by processor 5001 of the host system 5000 from long-term storage media devices 5011, such as a CD-ROM drive, tape drive or hard drive. The software program code may be embodied on any of a variety of known media for use with a data processing system, such as a diskette, hard drive, or CD-ROM. The code may be distributed on such media, or may be distributed to users from computer memory 5002 or storage of one computer system over a network 5010 to other computer systems for use by users of such other systems.

The software program code includes an operating system which controls the function and interaction of the various computer components and one or more application programs. Program code is normally paged from storage media device 5011 to the relatively higher-speed computer storage 5002 where it is available for processing by processor 5001. The techniques and methods for embodying software program code in memory, on physical media, and/or distributing software code via networks are well known and will not be further discussed herein. Program code, when created and stored on a tangible medium (including but not limited to electronic memory modules (RAM), flash memory, Compact Discs (CDs), DVDs, Magnetic Tape and the like is often referred to as a “computer program product”. The computer program product medium is typically readable by a processing circuit preferably in a computer system for execution by the processing circuit.

FIG. 19 illustrates a representative workstation or server hardware system in which the present invention may be practiced. The system 5020 of FIG. 19 comprises a representative base computer system 5021, such as a personal computer, a workstation or a server, including optional peripheral devices. The base computer system 5021 includes one or more processors 5026 and a bus employed to connect and enable communication between the processor(s) 5026 and the other components of the system 5021 in accordance with known techniques. The bus connects the processor 5026 to memory 5025 and long-term storage 5027 which can include a hard drive (including any of magnetic media, CD, DVD and Flash Memory for example) or a tape drive for example. The system 5021 might also include a user interface adapter, which connects the microprocessor 5026 via the bus to one or more interface devices, such as a keyboard 5024, a mouse 5023, a printer/scanner 5030 and/or other interface devices, which can be any user interface device, such as a touch sensitive screen, digitized entry pad, etc. The bus also connects a display device 5022, such as an LCD screen or monitor, to the microprocessor 5026 via a display adapter.

The system 5021 may communicate with other computers or networks of computers by way of a network adapter capable of communicating 5028 with a network 5029. Example network adapters are communications channels, token ring, Ethernet or modems. Alternatively, the system 5021 may communicate using a wireless interface, such as a CDPD (cellular digital packet data) card. The system 5021 may be associated with such other computers in a Local Area Network (LAN) or a Wide Area Network (WAN), or the system 5021 can be a client in a client/server arrangement with another computer, etc. All of these configurations, as well as the appropriate communications hardware and software, are known in the art.

FIG. 20 illustrates a data processing network 5040 in which the present invention may be practiced. The data processing network 5040 may include a plurality of individual networks, such as a wireless network and a wired network, each of which may include a plurality of individual workstations 5041, 5042, 5043, 5044. Additionally, as those skilled in the art will appreciate, one or more LANs may be included, where a LAN may comprise a plurality of intelligent workstations coupled to a host processor.

Still referring to FIG. 20, the networks may also include mainframe computers or servers, such as a gateway computer (client server 5046) or application server (remote server 5048 which may access a data repository and may also be accessed directly from a workstation 5045). A gateway computer 5046 serves as a point of entry into each individual network. A gateway is needed when connecting one networking protocol to another. The gateway 5046 may be preferably coupled to another network (the Internet 5047 for example) by means of a communications link. The gateway 5046 may also be directly coupled to one or more workstations 5041, 5042, 5043, 5044 using a communications link. The gateway computer may be implemented utilizing an IBM eServer™ System z® server available from International Business Machines Corporation.

Referring concurrently to FIG. 19 and FIG. 20, software programming code which may embody the present invention may be accessed by the processor 5026 of the system 5020 from long-term storage media 5027, such as a CD-ROM drive or hard drive. The software programming code may be embodied on any of a variety of known media for use with a data processing system, such as a diskette, hard drive, or CD-ROM. The code may be distributed on such media, or may be distributed to users 5050, 5051 from the memory or storage of one computer system over a network to other computer systems for use by users of such other systems.

Alternatively, the programming code may be embodied in the memory 5025, and accessed by the processor 5026 using the processor bus. Such programming code includes an operating system which controls the function and interaction of the various computer components and one or more application programs 5032. Program code is normally paged from storage media 5027 to high-speed memory 5025 where it is available for processing by the processor 5026. The techniques and methods for embodying software programming code in memory, on physical media, and/or distributing software code via networks are well known and will not be further discussed herein. Program code, when created and stored on a tangible medium (including but not limited to electronic memory modules (RAM), flash memory, Compact Discs (CDs), DVDs, Magnetic Tape and the like is often referred to as a “computer program product”. The computer program product medium is typically readable by a processing circuit preferably in a computer system for execution by the processing circuit.

The cache that is most readily available to the processor (normally faster and smaller than other caches of the processor) is the lowest (L1 or level one) cache and main store (main memory) is the highest level cache (L3 if there are 3 levels). The lowest level cache is often divided into an instruction cache (I-Cache) holding machine instructions to be executed and a data cache (D-Cache) holding data operands.

Referring to FIG. 21, an exemplary processor embodiment is depicted for processor 5026. Typically one or more levels of cache 5053 are employed to buffer memory blocks in order to improve processor performance. The cache 5053 is a high speed buffer holding cache lines of memory data that are likely to be used. Typical cache lines are 64, 128 or 256 bytes of memory data. Separate caches are often employed for caching instructions than for caching data. Cache coherence (synchronization of copies of lines in memory and the caches) is often provided by various “snoop” algorithms well known in the art. Main memory storage 5025 of a processor system is often referred to as a cache. In a processor system having 4 levels of cache 5053, main storage 5025 is sometimes referred to as the level 5 (L5) cache since it is typically faster and only holds a portion of the non-volatile storage (DASD, tape etc) that is available to a computer system. Main storage 5025 “caches” pages of data paged in and out of the main storage 5025 by the operating system.

A program counter (instruction counter) 5061 keeps track of the address of the current instruction to be executed. A program counter in a z/Architecture® processor is 64 bits and can be truncated to 31 or 24 bits to support prior addressing limits. A program counter is typically embodied in a PSW (program status word) of a computer such that it persists during context switching. Thus, a program in progress, having a program counter value, may be interrupted by, for example, the operating system (context switch from the program environment to the operating system environment). The PSW of the program maintains the program counter value while the program is not active, and the program counter (in the PSW) of the operating system is used while the operating system is executing. Typically, the program counter is incremented by an amount equal to the number of bytes of the current instruction. RISC (Reduced Instruction Set Computing) instructions are typically fixed length while CISC (Complex Instruction Set Computing) instructions are typically variable length. Instructions of the IBM z/Architecture® are CISC instructions having a length of 2, 4 or 6 bytes. The Program counter 5061 is modified by either a context switch operation or a branch taken operation of a branch instruction for example. In a context switch operation, the current program counter value is saved in the program status word along with other state information about the program being executed (such as condition codes), and a new program counter value is loaded pointing to an instruction of a new program module to be executed. A branch taken operation is performed in order to permit the program to make decisions or loop within the program by loading the result of the branch instruction into the program counter 5061.

Typically an instruction fetch unit 5055 is employed to fetch instructions on behalf of the processor 5026. The fetch unit either fetches “next sequential instructions”, target instructions of branch taken instructions, or first instructions of a program following a context switch. Modern Instruction fetch units often employ prefetch techniques to speculatively prefetch instructions based on the likelihood that the prefetched instructions might be used. For example, a fetch unit may fetch 16 bytes of instruction that includes the next sequential instruction and additional bytes of further sequential instructions.

The fetched instructions are then executed by the processor 5026. In an embodiment, the fetched instruction(s) are passed to a dispatch unit 5056 of the fetch unit. The dispatch unit decodes the instruction(s) and forwards information about the decoded instruction(s) to appropriate units 5057, 5058, 5060. An execution unit 5057 will typically receive information about decoded arithmetic instructions from the instruction fetch unit 5055 and will perform arithmetic operations on operands according to the opcode of the instruction. Operands are provided to the execution unit 5057 preferably either from memory 5025, architected registers 5059 or from an immediate field of the instruction being executed. Results of the execution, when stored, are stored either in memory 5025, registers 5059 or in other machine hardware (such as control registers, PSW registers and the like).

A processor 5026 typically has one or more units 5057, 5058, 5060 for executing the function of the instruction. Referring to FIG. 22A, an execution unit 5057 may communicate with architected general registers 5059, a decode/dispatch unit 5056, a load store unit 5060, and other 5065 processor units by way of interfacing logic 5071. An execution unit 5057 may employ several register circuits 5067, 5068, 5069 to hold information that the arithmetic logic unit (ALU) 5066 will operate on. The ALU performs arithmetic operations such as add, subtract, multiply and divide as well as logical function such as and, or and exclusive- or (XOR), rotate and shift. Preferably the ALU supports specialized operations that are design dependent. Other circuits may provide other architected facilities 5072 including condition codes and recovery support logic for example. Typically the result of an ALU operation is held in an output register circuit 5070 which can forward the result to a variety of other processing functions. There are many arrangements of processor units, the present description is only intended to provide a representative understanding of one embodiment.

An ADD instruction for example would be executed in an execution unit 5057 having arithmetic and logical functionality while a floating point instruction for example would be executed in a floating point execution having specialized floating point capability. Preferably, an execution unit operates on operands identified by an instruction by performing an opcode defined function on the operands. For example, an ADD instruction may be executed by an execution unit 5057 on operands found in two registers 5059 identified by register fields of the instruction.

The execution unit 5057 performs the arithmetic addition on two operands and stores the result in a third operand where the third operand may be a third register or one of the two source registers. The execution unit preferably utilizes an Arithmetic Logic Unit (ALU) 5066 that is capable of performing a variety of logical functions such as Shift, Rotate, And, Or and XOR as well as a variety of algebraic functions including any of add, subtract, multiply, divide. Some ALUs 5066 are designed for scalar operations and some for floating point. Data may be Big Endian (where the least significant byte is at the highest byte address) or Little Endian (where the least significant byte is at the lowest byte address) depending on architecture. The IBM z/Architecture® is Big Endian. Signed fields may be sign and magnitude, 1's complement or 2's complement depending on architecture. A 2's complement number is advantageous in that the ALU does not need to design a subtract capability since either a negative value or a positive value in 2's complement requires only an addition within the ALU. Numbers are commonly described in shorthand, where a 12 bit field defines an address of a 4,096 byte block and is commonly described as a 4 Kbyte (Kilo-byte) block, for example.

Referring to FIG. 22B, branch instruction information for executing a branch instruction is typically sent to a branch unit 5058 which often employs a branch prediction algorithm such as a branch history table 5082 to predict the outcome of the branch before other conditional operations are complete. The target of the current branch instruction will be fetched and speculatively executed before the conditional operations are complete. When the conditional operations are completed the speculatively executed branch instructions are either completed or discarded based on the conditions of the conditional operation and the speculated outcome. A typical branch instruction may test condition codes and branch to a target address if the condition codes meet the branch requirement of the branch instruction, a target address may be calculated based on several numbers including ones found in register fields or an immediate field of the instruction for example. The branch unit 5058 may employ an ALU 5074 having a plurality of input register circuits 5075, 5076, 5077 and an output register circuit 5080. The branch unit 5058 may communicate with general registers 5059, decode dispatch unit 5056 or other circuits 5073, for example.

The execution of a group of instructions can be interrupted for a variety of reasons including a context switch initiated by an operating system, a program exception or error causing a context switch, an I/O interruption signal causing a context switch or multi-threading activity of a plurality of programs (in a multi-threaded environment), for example. Preferably a context switch action saves state information about a currently executing program and then loads state information about another program being invoked. State information may be saved in hardware registers or in memory for example. State information preferably comprises a program counter value pointing to a next instruction to be executed, condition codes, memory translation information and architected register content. A context switch activity can be exercised by hardware circuits, application programs, operating system programs or firmware code (microcode, pico-code or licensed internal code (LIC)) alone or in combination.

A processor accesses operands according to instruction defined methods. The instruction may provide an immediate operand using the value of a portion of the instruction, may provide one or more register fields explicitly pointing to either general purpose registers or special purpose registers (floating point registers for example). The instruction may utilize implied registers identified by an opcode field as operands. The instruction may utilize memory locations for operands. A memory location of an operand may be provided by a register, an immediate field, or a combination of registers and immediate field as exemplified by the z/Architecture® long displacement facility wherein the instruction defines a base register, an index register and an immediate field (displacement field) that are added together to provide the address of the operand in memory for example. Location herein typically implies a location in main memory (main storage) unless otherwise indicated.

Referring to FIG. 22C, a processor accesses storage using a load/store unit 5060. The load/store unit 5060 may perform a load operation by obtaining the address of the target operand in memory 5053 and loading the operand in a register 5059 or another memory 5053 location, or may perform a store operation by obtaining the address of the target operand in memory 5053 and storing data obtained from a register 5059 or another memory 5053 location in the target operand location in memory 5053. The load/store unit 5060 may be speculative and may access memory in a sequence that is out-of-order relative to instruction sequence, however the load/store unit 5060 is to maintain the appearance to programs that instructions were executed in order. A load/store unit 5060 may communicate with general registers 5059, decode/dispatch unit 5056, cache/memory interface 5053 or other elements 5083 and comprises various register circuits, ALUs 5085 and control logic 5090 to calculate storage addresses and to provide pipeline sequencing to keep operations in-order. Some operations may be out of order but the load/store unit provides functionality to make the out of order operations to appear to the program as having been performed in order, as is well known in the art.

Preferably addresses that an application program “sees” are often referred to as virtual addresses. Virtual addresses are sometimes referred to as “logical addresses” and “effective addresses”. These virtual addresses are virtual in that they are redirected to physical memory location by one of a variety of dynamic address translation (DAT) technologies including, but not limited to, simply prefixing a virtual address with an offset value, translating the virtual address via one or more translation tables, the translation tables preferably comprising at least a segment table and a page table alone or in combination, preferably, the segment table having an entry pointing to the page table. In the z/Architecture®, a hierarchy of translation is provided including a region first table, a region second table, a region third table, a segment table and an optional page table. The performance of the address translation is often improved by utilizing a translation lookaside buffer (TLB) which comprises entries mapping a virtual address to an associated physical memory location. The entries are created when the DAT translates a virtual address using the translation tables. Subsequent use of the virtual address can then utilize the entry of the fast TLB rather than the slow sequential translation table accesses. TLB content may be managed by a variety of replacement algorithms including LRU (Least Recently used).

In the case where the processor is a processor of a multi-processor system, each processor has responsibility to keep shared resources, such as I/O, caches, TLBs and memory, interlocked for coherency. Typically, “snoop” technologies will be utilized in maintaining cache coherency. In a snoop environment, each cache line may be marked as being in any one of a shared state, an exclusive state, a changed state, an invalid state and the like in order to facilitate sharing.

I/O units 5054 (FIG. 21) provide the processor with means for attaching to peripheral devices including tape, disc, printers, displays, and networks for example. I/O units are often presented to the computer program by software drivers. In mainframes, such as the System z® from IBM®, channel adapters and open system adapters are I/O units of the mainframe that provide the communications between the operating system and peripheral devices.

Further, other types of computing environments can benefit from one or more aspects of the present invention. As an example, an environment may include an emulator (e.g., software or other emulation mechanisms), in which a particular architecture (including, for instance, instruction execution, architected functions, such as address translation, and architected registers) or a subset thereof is emulated (e.g., on a native computer system having a processor and memory). In such an environment, one or more emulation functions of the emulator can implement one or more aspects of the present invention, even though a computer executing the emulator may have a different architecture than the capabilities being emulated. As one example, in emulation mode, the specific instruction or operation being emulated is decoded, and an appropriate emulation function is built to implement the individual instruction or operation.

In an emulation environment, a host computer includes, for instance, a memory to store instructions and data; an instruction fetch unit to fetch instructions from memory and to optionally, provide local buffering for the fetched instruction; an instruction decode unit to receive the fetched instructions and to determine the type of instructions that have been fetched; and an instruction execution unit to execute the instructions. Execution may include loading data into a register from memory; storing data back to memory from a register; or performing some type of arithmetic or logical operation, as determined by the decode unit. In one example, each unit is implemented in software. For instance, the operations being performed by the units are implemented as one or more subroutines within emulator software.

More particularly, in a mainframe, architected machine instructions are used by programmers, usually today “C” programmers, often by way of a compiler application. These instructions stored in the storage medium may be executed natively in a z/Architecture® IBM® Server, or alternatively in machines executing other architectures. They can be emulated in the existing and in future IBM® mainframe servers and on other machines of IBM® (e.g., Power Systems servers and System x® Servers). They can be executed in machines running Linux on a wide variety of machines using hardware manufactured by IBM®, Intel®, AMD™, and others. Besides execution on that hardware under a z/Architecture®, Linux can be used as well as machines which use emulation by Hercules, UMX, or FSI (Fundamental Software, Inc), where generally execution is in an emulation mode. In emulation mode, emulation software is executed by a native processor to emulate the architecture of an emulated processor.

The native processor typically executes emulation software comprising either firmware or a native operating system to perform emulation of the emulated processor. The emulation software is responsible for fetching and executing instructions of the emulated processor architecture. The emulation software maintains an emulated program counter to keep track of instruction boundaries. The emulation software may fetch one or more emulated machine instructions at a time and convert the one or more emulated machine instructions to a corresponding group of native machine instructions for execution by the native processor. These converted instructions may be cached such that a faster conversion can be accomplished. Notwithstanding, the emulation software is to maintain the architecture rules of the emulated processor architecture so as to assure operating systems and applications written for the emulated processor operate correctly. Furthermore, the emulation software is to provide resources identified by the emulated processor architecture including, but not limited to, control registers, general purpose registers, floating point registers, dynamic address translation function including segment tables and page tables for example, interrupt mechanisms, context switch mechanisms, Time of Day (TOD) clocks and architected interfaces to I/O subsystems such that an operating system or an application program designed to run on the emulated processor, can be run on the native processor having the emulation software.

A specific instruction being emulated is decoded, and a subroutine is called to perform the function of the individual instruction. An emulation software function emulating a function of an emulated processor is implemented, for example, in a “C” subroutine or driver, or some other method of providing a driver for the specific hardware as will be within the skill of those in the art after understanding the description of the preferred embodiment. Various software and hardware emulation patents including, but not limited to U.S. Pat. No. 5,551,013, entitled “Multiprocessor for Hardware Emulation”, by Beausoleil et al.; and U.S. Pat. No. 6,009,261, entitled “Preprocessing of Stored Target Routines for Emulating Incompatible Instructions on a Target Processor”, by Scalzi et al; and U.S. Pat. No. 5,574,873, entitled “Decoding Guest Instruction to Directly Access Emulation Routines that Emulate the Guest Instructions”, by Davidian et al; and U.S. Pat. No. 6,308,255, entitled “Symmetrical Multiprocessing Bus and Chipset Used for Coprocessor Support Allowing Non-Native Code to Run in a System”, by Gorishek et al; and U.S. Pat. No. 6,463,582, entitled “Dynamic Optimizing Object Code Translator for Architecture Emulation and Dynamic Optimizing Object Code Translation Method”, by Lethin et al; and U.S. Pat. No. 5,790,825, entitled “Method for Emulating Guest Instructions on a Host Computer Through Dynamic Recompilation of Host Instructions”, by Eric Traut, each of which is hereby incorporated herein by reference in its entirety; and many others, illustrate a variety of known ways to achieve emulation of an instruction format architected for a different machine for a target machine available to those skilled in the art.

In FIG. 23, an example of an emulated host computer system 5092 is provided that emulates a host computer system 5000′ of a host architecture. In the emulated host computer system 5092, the host processor (CPU) 5091 is an emulated host processor (or virtual host processor) and comprises an emulation processor 5093 having a different native instruction set architecture than that of the processor 5091 of the host computer 5000′. The emulated host computer system 5092 has memory 5094 accessible to the emulation processor 5093. In the example embodiment, the memory 5094 is partitioned into a host computer memory 5096 portion and an emulation routines 5097 portion. The host computer memory 5096 is available to programs of the emulated host computer 5092 according to host computer architecture. The emulation processor 5093 executes native instructions of an architected instruction set of an architecture other than that of the emulated processor 5091, the native instructions obtained from emulation routines memory 5097, and may access a host instruction for execution from a program in host computer memory 5096 by employing one or more instruction(s) obtained in a sequence & access/decode routine which may decode the host instruction(s) accessed to determine a native instruction execution routine for emulating the function of the host instruction accessed. Other facilities that are defined for the host computer system 5000′ architecture may be emulated by architected facilities routines, including such facilities as general purpose registers, control registers, dynamic address translation and I/O subsystem support and processor cache, for example. The emulation routines may also take advantage of functions available in the emulation processor 5093 (such as general registers and dynamic translation of virtual addresses) to improve performance of the emulation routines. Special hardware and off-load engines may also be provided to assist the processor 5093 in emulating the function of the host computer 5000′.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiment with various modifications as are suited to the particular use contemplated. 

What is claimed is:
 1. A computer program product for providing access to adapters in a computing environment, the computer program product comprising: a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: executing, by a processor, a guest instruction issued by a guest processor, the guest instruction comprising a request to access an adapter of the computing environment, and the guest processor being hosted by a host operating system; determining whether the guest instruction is permitted to directly access the adapter; based on the guest instruction being permitted to directly access the adapter, the execution directly accessing one or more address spaces of the adapter without host intervention of the host operating system; and based on the guest instruction not being permitted to directly access the adapter, the execution causing an intercept to the host operating system.
 2. The computer program product of claim 1, wherein the determining comprises determining whether the host operating system enabled the guest processor for interpretation of the guest instruction and wherein the execution directly accesses an address space of the adapter, the accessing comprising a read or a write operation.
 3. The computer program product of claim 1, wherein the method further comprises: determining by the host operating system that it wants to intervene in execution of the guest instruction; and intercepting by the host operating system execution of the guest instruction, based on the host operating system determining it wants to intervene.
 4. The computer program product of claim 1, wherein the method further comprises performing one or more actions, by the host operating system on behalf of the guest processor, to enable the guest instruction to directly access the adapter.
 5. The computer program product of claim 4, wherein the one or more actions comprise: authorizing the guest processor for interpretation of one or more specific privileged instructions; and enabling the guest processor for interpretation of one or more specific privileged instructions.
 6. The computer program product of claim 1, wherein the determining comprises determining whether the guest processor issuing the guest instruction is authorized to access the adapter.
 7. The computer program product of claim 6, wherein the determining whether the guest processor is authorized uses an authorization token to make the determination.
 8. The computer program product of claim 7, wherein the determining whether the guest processor is authorized comprises comparing the authorization token stored in a specified location with an authorization token associated with that guest processor, wherein equality indicates authorization.
 9. The computer program product of claim 6, wherein the determining whether the guest instruction is permitted further comprises: determining whether the guest processor is enabled for adapter access interpretation; determining whether the adapter is enabled for adapter access interpretation; and determining whether a function handle associated with the adapter and specified in the request is enabled, wherein the guest processor is permitted to access, based on the guest processor being authorized, the guest processor being enabled for adapter access interpretation, the adapter being enabled for adapter access interpretation and the function handle being enabled.
 10. A computer system for providing access to adapters in a computing environment, the computer system comprising: a memory; and a processor in communications with the memory, wherein the computer system is configured to perform a method, said method comprising: executing, by a processor, a guest instruction issued by a guest processor, the guest instruction comprising a request to access an adapter of the computing environment, and the guest processor being hosted by a host operating system; determining whether the guest instruction is permitted to directly access the adapter; based on the guest instruction being permitted to directly access the adapter, the execution directly accessing one or more address spaces of the adapter without host intervention of the host operating system; and based on the guest instruction not being permitted to directly access the adapter, the execution causing an intercept to the host operating system.
 11. The computer system of claim 10, wherein the determining comprises determining whether the host operating system enabled the guest processor for interpretation of the guest instruction and wherein the execution directly accesses an address space of the adapter, the accessing comprising a read or a write operation.
 12. The computer system of claim 10, wherein the method further comprises: determining by the host operating system that it wants to intervene in execution of the guest instruction; and intercepting by the host operating system execution of the guest instruction, based on the host operating system determining it wants to intervene.
 13. The computer system of claim 10, wherein the method further comprises performing one or more actions, by the host operating system on behalf of the guest processor, to enable the guest instruction to directly access the adapter.
 14. The computer system of claim 10, wherein the determining comprises determining whether the guest processor issuing the guest instruction is authorized to access the adapter.
 15. The computer system of claim 14, wherein the determining whether the guest processor is authorized uses an authorization token to make the determination.
 16. The computer system of claim 14, wherein the determining whether the guest instruction is permitted further comprises: determining whether the guest processor is enabled for adapter access interpretation; determining whether the adapter is enabled for adapter access interpretation; and determining whether a function handle associated with the adapter and specified in the request is enabled, wherein the guest processor is permitted to access, based on the guest processor being authorized, the guest processor being enabled for adapter access interpretation, the adapter being enabled for adapter access interpretation and the function handle being enabled.
 17. A method of providing access to adapters in a computing environment, said method comprising: executing, by a processor, a guest instruction issued by a guest processor, the guest instruction comprising a request to access an adapter of the computing environment, and the guest processor being hosted by a host operating system; determining, by the processor, whether the guest instruction is permitted to access the adapter; based on the guest instruction being permitted to directly access the adapter, the execution directly accessing one or more address spaces of the adapter without host intervention of the host operating system; and based on the guest instruction not being permitted to directly access the adapter, the execution causing an intercept to the host operating system.
 18. The method of claim 17, further comprising: determining by the host operating system that it wants to intervene in execution of the guest instruction; and intercepting by the host operating system execution of the guest instruction, based on the host operating system determining it wants to intervene.
 19. The method of claim 17, wherein the determining comprises determining whether the guest processor issuing the guest instruction is authorized to access the adapter.
 20. The method of claim 19, wherein the determining whether the guest instruction is permitted further comprises: determining whether the guest processor is enabled for adapter access interpretation; determining whether the adapter is enabled for adapter access interpretation; and determining whether a function handle associated with the adapter and specified in the request is enabled, wherein the guest processor is permitted to access, based on the guest processor being authorized, the guest processor being enabled for adapter access interpretation, the adapter being enabled for adapter access interpretation and the function handle being enabled. 